Hey Zo,
I am not clear on what your objective is.
If you want to count how many pixels are there for each possible color combination you can run this script in Matlab -
A = imread('image.jpg')
b=size(A)
col=zeros(256,256,256);
for i=1:b(1)
for j=1:b(2)
col(A(i,j,1)+1,A(i,j,2)+1,A(i,j,3)+1)=col(A(i,j,1)+1,A(i,j,2)+1,A(i,j,3)+1)+1;
end
end
