Yes. You are right.  :o It should not happened like the way you just pointed out. :P  This is what need to be improved. ? hope someone can find out a better way of doing it (I will try to think about it,too.).    :-[

The frequency response for electromagnetic wave to our eye is not a linear function. The color mixing for vision is not a simple process.
[img]http://www.phy.ntnu.edu.tw/oldjava/image/rgb.gif[/img]
[img]http://www.phy.ntnu.edu.tw/demolab/everydayPhysics/lightNeye.gif[/img]