It's somewhat known now-a-days that a number of Pokémon have had their shiny colours changed over the games and generations - particularly those around early on (Gen 1, Gen 2, Gen 3). Some of these are subtle - a slight change in saturation across generations, but others are somewhat more dramatic. Originally, I was going to write about a wider array of games, but here I'd like to focus on the interesting shiny shenanigans present in the Gamecube games, Pokémon Colosseum and Pokémon XD: Gale of Darkness.
Before we begin, I would like to provide image sourcing/thanks - the Pokémon sprites you see are taken from the Pokémon Database; the Pokémon Stadium 2 shiny images are taken from the Blue Moon Falls Stadium gif archive. Images from Colosseum and XD are taken by myself.
Starting off with one of my favourite Pokémon as an example, Scizor's original shiny was a slightly greenish-yellow - the hexcode of it's body colour being #B5B542 ■ which is pretty much in the domain of yellow. Colour-picking it's shiny colour from Pokémon Home however, gives us a body colour of #CBFA55 ■ - very solidly in the domain of lime green. But the main difference comes from Scizor's shiny in Pokémon Colosseum and Pokémon XD: Gale of Darkness, where it appears to be intended to be gold. It's main colour is around hex #F0D34B ■ - the most yellow and most vibrant of it's shinies. It's shiny colour in Generation 3 was around #B0B840 ■ - very close to it's Generation 2 shiny colour (and due to the hardware of the Gameboy Advance, Generation 3 did not have many limitations of sprite colours) - so was this an error? Or were Genius Sonority (the developers behind Coloseum and XD) given creative freedom on some of the shiny palettes?
Scizor doesn't appear for capture in the western version of Pokémon Colosseum - but is available as an e-Reader exclusive Shadow Pokémon in the Japanese version - so let us take a look at the other Shadow Pokémon available via e-Reader, and their shinies.
In terms of it's wool Mareep's shiny was, in Generation 2, a very vibrant pink - (#FF84FF ■) - then mellowed out in Generation 3 to a more dusty-peach pink (#F8D0C8 ■), and then made vibrant once again in Generation 4 (#FFCEFF ■). In Pokémon Stadium 2, it's shiny forms wool is roughly around #FD85DC ■ - visually inbetween it's Gen 2 and Gen 3 palettes. Interestingly it's body colour goes to a vibrant green! Inconsistent with all it's other shinies.
In Colosseum and XD: Gale of Darkness, we can observe the colour of it's wool to now be a very vibrant #F67789 ■, far closer to the Generation 2 and Generation 4 palettes, but still extremely vibrant compared to it's Generation 3 shiny colours.
Note - Mareep is available as a catchable Shadow Pokémon in Pokémon XD: Gale of Darkness
Togepi's shiny is usually subtle but interesting. Generation 2's utilizes black to cover blue in the regular pallete, and black to cover red in the shiny palette due to colour limitations - From it's normal palette to shiny pallete, it's red patterns switch to blue. In Gen 3, it's skin colour was subtle between it's normal palette (#F8F0A8 ■) and it's shiny palette (#F8E0A8 ■) (if those hexcodes look similar - it's one letter difference, the third letter). Here we once again see the difference in the patterns being swapped between blue and red.
It's Colosseum and XD: Gale of Darkness shiny I can only describe as a tea-stained egg (affectionately), with dramatically darker egg shell and skin colour, and instead of the usual red-to-blue switch, the triangular patterns darken - as far as I've seen, this is the only instance of shiny Togepi where the pattern colour doesn't switch.
Note - Togepi is available as a Gift Pokémon in Pokémon XD: Gale of Darkness, as well as being an e-Reader Shadow Pokémon in Pokémon Colosseum.
So those are the e-Reader Shadow Pokémon, let's take a look at some of the Shadow Pokémon available in regular gameplay.
First up is Heracross because I love bug mons, and at a quick glance it's shiny is different but not too wild - except what's going on with it's abdomen? Regular Heracross in the Gamecube games is blue across it's whole body - as Heracross always appears - but in it's shiny form, it's horn, head, and limbs appear as a highly saturated blue, with it's abdomen being a bright purple - as far as I can find, no other depiction of shiny Heracross has this two-tone colouration to it's body. The closest (and this is likely a coincidence) is it's Mega Form, which changes the colour of it's elitra and scutellum to gold, whereas it's body turns pink-purple. This is however fairly accurate to a large number of real-world beetles where their elytra (wing-covers) are a different colour to their abdomen. While not all of them have the same dramatically different colours as Heracross does, there are certainly Dynastinae (rhinoceros beetles) which have colour differences in the same areas (eg. Eupatorus gracilicornis, Dynastes hercules).
So we're already off to a good start, let's move away from Bug-types and take a look at Ursaring. Another odd change - in Generation 2, 3, and all others, it's shiny appears a vibrant green colour, whereas in the Gamecube games, it's extremely dark with a very slight green tint to it's main body colour - though it's muzzle, claws, and circle-pattern do appear noticibly more green. It's more akin to it's Stadium 2 shiny, but that is a far lighter colour overall, and the colour of it's muzzle matches it's Gen 2 shiny palette much closer if a bit darker - #D6EFCE ■ and #B2CEAA ■.
Moving onto some of the Generation 3 Shadow Pokémon with interesting shiny differences - Absol at first looks extremely close to it's Gen 3 shiny - but with an exception. It's claws remain a dark blue - which really stands out against it's red-tinted fur. Additionally it's GBA shiny palette colours it's eyes blue, whereas it's Colosseum & XD palette appears to give the model red eyes. Other than that, it's a fairly good match visually.
Metagross' is very cool - rather than the neutral grey-silver of it's usual shiny, it's tinted red-ish (#615252 ■) with interesting interactions with the light source giving a hint of it's original green-blue colour - making it look iridescent (see below embeded video to see if in motion). The cross across it's face also shifts to white.
For the most part though (in terms of Shadow Pokémon), Generation 3 shinies aren't too different between their Gameboy Advance depiction and their Gamecube depiction - Of course I have no idea how the development of the games proceeded and what communication was made between GameFreak, Genius Sonority, and Nintendo so it's difficult to know why some of the shinies are completely accurate, and why some aren't. These days, companies involved with production of Pokémon games are given very strict guidelines on how to depict Pokémon.
Perhaps one of the most stricking Shiny differences comes from the legendary leopard-like beast, Suicune. It's shiny has changed across Generations, going from a pastel lilac (#CEC5FF ■) in Gen 2, to having navy mane in Generation 3 (#3888D8 ■), then a more saturated blue mane in Generation 4 (#378CFC ■). It's mane in the Gamecube games however turns a stark black (#29302A ■). Raikou and Entei's shinies however are fairly faithful to the Generation 3 shiny palettes. This is particularly odd, as the Gamecube games notoriously use the same 3D models as Pokémon Stadium 1 and Pokémon Stadium 2 for most of the Pokémon. At least, they use the same meshes and largely the same animations for most - there are a few outliers here; an example being Wigglytuff whose mesh and textures are different. We're going to need to rely on the rips over on the models-resource;
The Pokémon Stadium 1 model here comes from the Pokédex Mode as Wigglytuff was not playable in Japanese Stadium 1 - the models here are all slightly different (compare overall body shape of each, as well as particularly the ear shape), with the textures all being notably different (Compare S1 and S2's eyes, and S2 and Colo's white abdomen).
Another example here with Meowth, whilst S2 and Colo look the same in terms of the mesh (the overall shape of the 3D model), looking closely at the face shows that the textures at the very least have been redrawn with features such as Meowth's eyes and mouth being repositioned to better match how Meowth is usually proportioned. In particular compare the size of Meowth's fangs, and wideness of the mouth and it's very clear the texture was re-done for Colosseum. Another quick example is Articuno's model from Pokémon Stadium 2 and it's model from Colosseum - count the number of feathers on it's wings (8 vs 9) and it's clear that not all Pokémon in Colosseum use their Stadium/Stadium 2 models, which may account for some of the shiny colours being off for Pokémon from Generation 1 and 2. However, please keep in mind, this is just speculation unless someone from Genius Sonority ever provides details (extremely unlikely).
The previous examples are all from Pokémon Colosseum, so let's look at a few Poké featured as Shadow mons in XD: Gale of Darkness
Magcargo's shiny body colour was #635AE6 ■ in Generation 2, far closer to blue than purple, whereas it's shiny body colour in Generation 3 was #E8B0E8 ■ - undoubtably in the pink range. It's shiny in the Gamecube games however became an vibrant deep purple - not the most dramatic change on this list, but still worth a mention especially conisdering it isn't particularly similar to either it's Gen 2 colour or Gen 3 colour.
Lapras sees a larger change in colouration - it's Generation 2 shiny a mixture of purple and pink (#FF6BFF ■ and #845AFF ■), and it's Generation 3 shiny a much more subtle lilac and dusty-pink (#E8C8D0 ■ and #A898E0 ■). It's Stadium 2 shiny bright green and indigo (#CDFEC5 ■ and #81568C ■) Not Colosseum and XD: Gale of Darkness though - it's body colour turns to an almost neon teal (#39C3C3 ■), and it's underbelly a blush-red, almost a reddish-brown (#A27474 ■). It's shiny bares no resemblence to any of it's previous colours, but it's very nice aesthetically.
Azumarill's shiny in the Gamecube games is bizarrely different - it's largely been consistent up until now, with only the blue ears of it's Stadium 2 shiny standing out - but Colosseum ditches the gold for green - not even a yellow-ish green just a straight up green (#008029). The colour on it's lower half is yellow (#E1DA2E), but still the bulk of it's colour is still wildly off (even it's eyes turn from gold to green!)
Miltank is not the most egregious example of odd Gamecube shinies, but I still think it deserves a mention. Both it's Gameboy game shinies and Stadium 2 shiny I would class as firmly in the realm of purple, whereas it's Gameboy Advance game shinies are a very pastel powdered blue - it's Gamecube colouration is a much more steel-y blue, with red eyes and tinted-red horns. It's a surprisingly nice colour but still an odd choice in comparison to it's purple Gen 2 shiny and it's powder blue Gen 3 shiny.
A shiny with a special place in my heart, Illumise was the first shiny Pokémon I ever encountered, other than the Red Gyarados of the Lake of Rage. I still have her! ALLE is her nickname, though where that nickname came from I have no idea. I remember bringing her up through to Pokémon Colosseum the first time I could connect my Ruby cartridge to it, and behold! This... shiny? I prefer not to be negative, but unfortunately Illumise's shiny looks like the regular colouration with a slight yellow filter over it - even it's antenna and the yellow around it's neck stay the same rather than turning red, and unfortunately it just doesn't look good. There are a few other Gen 3 with this issue; looking more akin to having an overlay of thor shinies colouration being put over their texture (eg. Castform, which loses it's golden mask; Dustox, Volbeat, Lotad, etc.)
Before we end off, here's a bunch of Gen 3 shinies with some interesting shiny differences; plus Flygon who unfortunately suffers from the "just put an overlay on the regular colours" issue);
To finish off let's look at Mewtwo's shiny - an interesting journey for sure. The Colosseum and XD palette isn't too dissimilar from it's Generation 2 shiny colour - lighter and slightly muted but definitely around the same colour. Mewtwo's Stadium 2 shiny however is a blue-black, with it's Gen 3 Gameboy Advance shiny being a bright green. Whilst the bright green shiny is iconic to it now-a-days, the muted beige-yellow-ish colour doesn't look too bad, and appears to be an attempt at matching the Gen 2 palette.
These are, of course, not the only shiny oddities in the Gamecube games, for sure; as mentioned previously there are a number of Pokémon akin to Illumise and Flygon where the shiny appears to be the regular colour with a subtle overlay; and there are a handful more with shinies which don't match any previous shiny palettes - I'm also far from the first person to notice this, and I was hoping that looking into them like this would allow us to find some reasoning behind the changes. I've also discovered a number of shiny oddities between the Gold, Silver, and Crystal colour palettes VS. the Stadium 2 shinies, but Stadium has historically done some funky things with Pokémon colour so it feels somehow less surprising (though I will definitely do a page on this in the future!)