I don't know about the official artwork, but they certainly don't match the anime artwork.
After 5 generations of games and many seasons of anime with the more vibrant colors, you don't just go and change the in-game character models to better match official artwork that is over a decade old. They waited far too late to do it, people had already got used to the darker colors so it was a jarring change for many.
Reminds of a situation that I noticed in the gen 4 anime.
Pikachu generally looked much more washed out and pale than he used to in it, and then they fixed the colours in the gen 5 anime and so on:
Diamond and Pearl Series:
Black and White Series:
Last edited by Green098 - on 20 May 2018