For Euclidean distance it seems to be in the neighborhood of (59, 250, 60) which is a bright green, although of course Euclidean distance is not perceptual distance. The blue at (57, 42, 214) also is up there.
Pick points at random, then use a general-purpose optimization method (the optim function in R) to find local maxima. I don’t claim this is a good way to do it.
