I did finally get it to work by separating the colors like you said... Do you know the formula to get this number in the 0-255 scale? It seems to be in 16M scale and is only a gray image.... I'm trying to speed it up some...

I've used alphablend and some others, but I'm creating a mean image and standard deviation image that will be used in my programs. This won't need to be done very often, so the speed isn't real critical. Thanks!