I think they changed it of their own volition for the wings. I say this because they made a series of general aesthetic changes to the opening, and even in the finished character designs, King's wings are coloured black. I think it was more of a matter of the opening being unfinished and a mistake getting past than Oda in that scenario.
Also, I wouldn't really say the skin tone pre-time skip was a mistake(her colouring was better then than it is now). Its also worth noting Oda changing the colouring things to start off. For example, Kuma was originally coloured orange, but that was changed to black. Gear 4th originally had blue haki in the covers, but in the snakeman cover, his shown with the more familiar red haki.