>>43154820Gengar's coloration from the anime has always been the one on top. However, Sugimori has changed the coloration of Gengar in the games to a lighter shade of purple as of FRLG. The Gengar in every game from that point on reflect the new coloration.
Light purple Gengar is supposed to be the official coloration of this Pokemon. Nevertheless, the anime continued to use the older dark purple coloration for a while, up until the point where the Gengar that Ash would eventually catch appears for the first time. This coloration scheme to match the official coloration was likely ordered by the higher-ups at The Pokemon Company, and it served as a hint that this Gengar would be caught by Ash.
