>>34507989I believe the reason is because Gamefreak used the Sugimori art. But, the issue with that is the Sugi art paints the pokemon in neutral light- that is, light if the Pokemon was in a pure white room.
The problem with this is very rarely are Pokemon in white rooms, and naturally they would take on the colour of their surroundings because of diffuse lighting. This pic is an example of Parasect under different lighting conditions. The washed out one looks acceptable in a white room, whereas the saturated orange one (similar to
>>34506725 ) looks good when next to a volcano.
None of this would be an issue if the game handled lighting better, I feel.