I HATE when people say this.
The models are NOT washed out - the old sprites were just WAY over saturated.
The new color pallet is made to better match the official artwork.
It doesn't really matter if the pokemon were originally intended to be less colorful.
They ARE washed out compared to the DS sprites and i do hope gamefreak makes them more colorful in the next game.
No, they are color-accurate compared to the DS sprites. And I'm very sure they'll stay that way, as there's literally no reason to go back after making the assertive effort to color correct.
And the anime's colors doesn't matter. I'm talking about the official released artwork. The "Sugimori (and co.)" art. Pokemon was designed to be a franchise of pastels, not primaries. I'm glad they don't go back as the over saturation would look absolutely garish in 3D when in context of equally saturated environments and not isolated in white backgrounds, and I hope they never will again. I also hope they don't get rid of the outlines, because that's another weird "fix" people keep asking for, like it's literally supposed to look like the incredible artwork come to life. In every way.
Then again, in an era where the fan requested "all villains" team concept actually manifested as Rainbow Rocket, which is literally the worst fan fiction, who knows what they're willing to do now. Maybe along with a new hyper saturated colorscheme, Gen 8 will bring the much requested Kanjohennohnovaloslola region with 48 gyms, 8 trials, 5 Pokemon leagues, and a raised level cap of 500 to fit it all.
Ok that was a tangent, but tl;dr - I prefer pastels and lines.