Vermilion Juiceさんのイラストまとめ

The end of a long journey.
Mew was originally paler, almost white, just the tips of its tail and feet exhibited its skin color; thus even its shiny was primarily white. Apart from this, Mew's sky blue never needed to change.

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato

Shiny Lapras in the past was pretty similar to the current appearance, just more pinkish overall, even on the shell. That's because of the graphical limitations of the Game Boy Color we know very well by now.

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato

Diglett and Dugtrio's only features were their noses: as for Venonat family, they were purple instead of the modern blue. Their skin was subtly more vivid too.
GBC palette limitations influenced even the soil color.

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato

Vulpix was a bit darker than its following shiny sprites, while Ninetales still had a pinch of lilac in its fur. Modern Ninetales is silver, instead.

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato

Nidoran♂ line continues the parallelism with its female counterpart: their body colors is similar to the non-shiny female variants. As such, the matter with the spots on Nidoran and Nidorino is along the lines of their opposites.

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato

The old shiny Sandshrew was grey before turning lime green / celadon in gen 3.
Sandslash was just as cool as its modern look with its army green body and rust colored spikes. I really love its colors in both of its appearances!

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato

Pikachu's usually red and brown elements was just purple.
Raichu, on the other hand, was almost gold and silver in color.

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato

The shiny forms of Pidgey family's blatantly golden nowadays.
Old Pidgey was less vibrant and more or less the same goes with Pidgeotto that was brownish in the past. Finally Pidgeot was olive green with pink streaks in its hair.

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato

Charmeleon was pinkish red rather than yellow like Charmander and the modern Charmeleon.
On the other hand, Charizard was famous for being much less edgy compared to now: amethyst and jade was its colors, as if it was an idol.

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato

Bulbasaur line wasn't so different from the modern one after all.
The main differences were the spots on Bulbasaur and Ivysaur's bodies that were black instead of dark green. Venusaur's pistil also was white rather than yellow.

🇬🇧#shiniesoffuturepast 🇮🇹#shinydiunfuturopassato