I let the example chess program run 4 times and the each time white (the un-optimized version) won. Granted that is not enough times to prove anything but funny anyway.
White has first-mover advantage, maybe your browser does not support asm.js? At least on Firefox blue won, but the page load so slow I don't care to repeat the experiment right now.
Your right, my browser does not support asm.js. I was still expecting 50/50 but the white advantage seems to be very overwhelming in practice.