coding and color

What prevents CC from allowing each user to implement their own color scheme?* In other words, why do I only receive some code saying 'red = red only;--but no options within the code which allow the user to change the brightness/hue of red?
Is this possible, but more difficult to code? Or is it impossible with CC's given 'engine' or whathever the code's platform/whatever is?
Is this possible, but more difficult to code? Or is it impossible with CC's given 'engine' or whathever the code's platform/whatever is?