ok thats addictive, so .. it would be....
yello + yello = yelloe right :S HEHE
well. i think you have to work with hue channel numbers or maybe not, like, a cicle is 360º degrees right.. on your circle the max is 255.. now you have to know that 255+ 10 wont be 265 but 005 in a color channel i think :S
and 255 + 10 should be 255 again, because thats the max of the variable of color ...
But anyway follow my tip!
you to a 260 or 360 to be your 255 of red for
right to you have to write a function for that...
but that aint work.
CHECK THIS SOURCE! with CODE examples.. (i think it might be handy...) :
HERE