Re: Yellow: Spearow
That's interesting... It is possible for Pokemon caught in Red, Blue and Yellow to be Shiny, but it's only visible once you trade the Pokemon to Gold/Silver and subsequent games.
Are you sure it's really different to other Spearow in Yellow? Some of the sprites in Red, Blue and Yellow are oddly coloured anyway, but they should still be the same for Pokemon of the same species. Anyway if you're sure it's different then I don't know what to tell you haha. If you have Gold, Silver or Crystal, you could try trading it to one of them and seeing if it's actually Shiny?