That is the yellow one, I believe two pictures are showing the same aircraft.
The belly picture only appears less saturated because it was at the shady side and the sky was brighter, which affected white balance of the camera.
I will stop here, but I have my doubt. Unless, in a way I can't understand, that the photo was really "twisted". Because, as I know saturation change only lead to the shade change, from deep gray to light gray, or deep yellow to light yellow or even milky white, but never reverse the color temperate, yellow and blue/green (J-20's real paint color) are opposite, they don't "bleed" into one another unless something like colored filter or PS are applied. Anyway, only my understanding.
Another thing is that, we have seen three J-20s at Chengdu air field, one gray and two yellow, don't you think that we are seeing two aircrafts?