I just realized the sprites in Gen II have 4 colors: white, black, and 2 more. This is the only example I could find, but it's enough to get the point across. (
Six-Letter Pokémon (Gen. 2) (Picture Click) Quiz - By beforever
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List of Gen 2 Pokemon (Johto Pokedex) - Pokemon Gold, Silver and Crystal Guide - IGN
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Old Back The 2nd Generation Promo Card 1999 Released Pokemon Cards | eBay
pokemon gen 2 accouding to my brother by ConCloud2017 on DeviantArt
Let's Talk About Pokemon! — Let's Talk About Pokemon - Gen 2