I have seen that picture before, and have always wondered how true the colors are. I have seen some other pics of white bastis that have blue tints to them or a few blue marks... but never a whole blue basti (except for this pic). I just wonder how come we haven't seen more pics of whole blue ones if they do occur? However, I wouldn't say that there isn't a blue basti for sure as there is just so much variation in pumilio... and cause I haven't been to the island myself .
I agree that the colors are off, but do you think they are that off to make the one white frog so blue? I would hope they'd try to correct the color, but they probably didn't. Anyways, here is another basti with blue:
Coloration: Typical coloration in Costa Rica and mainland Panamá may be red with blue "pants". Colors on the Bocas del Toro Archipelago can vary from island to island and some islands may contain multiple color morphs. Observed colors include red, orange, yellow, green, blue, purple, white, and black, with all shades in between.
I'd guess it is blue. As far as the coloration being off, I know the photographer and I doubt he would publish and put his name on a poor photo.