Can you try adding "rgb(255,255,255)" to the array, instead of just "255,255,255"?
Not sure if it works, but give it a try
Another thing worth mentioning, is what rgb(r,g,b) actually does. It's just a calculation:
r + (g * 256) + (b * 256 * 256)
So for instance, rgb(255,255,255) = 16777215
So you can actually put 16777215 in your array and that's equal to rgb(255,255,255) which is white