I think everybody is forgetting that this is based off of Dragonball, and not Dragonball Z... The Piccolo in this movie is King Piccolo from the later half of Dragonball. There is no "Piccolo JR" or a good side, or anything along those lines.
That being said, they've probably decided to make the look of King Piccolo more distinct from good Piccolo should they make a sequel. I think it might be a good thing that he looks different.
I should also mention that if anyone remembers Fox's movie "Alien Resurrection", the Humalien was initially created with a giant vagina going up to it's chest, and in post production they digitally removed it. Piccolo may be yellow for the time being <_<... !@#$% he may not be green for the sake of greenscreening... and they'll change him in post production... We *don't know*.