% Display "all" colors combinations between full red and full blue.
% Use a granularity of 1/4.

close all
axis([0 1.25 0 1.25])
axis equal off
hold on

gran= 0.25;  % granularity for red and blue values
             % hold green value constant at 0
for r= 0:gran:1
    for b= 0:gran:1
        c= [r 0 b];
        % draw the color (represent red on x-axis, blue on y-axis)
          x= [r r+gran r+gran r];
          y= [b b      b+gran b+gran];
          fill(x,y, c)
    end
end

hold off