Selective Color - finally I try to learn it

Still don't know which is the right program to do the job, especially mac native and not expensive adobe photoshop, but here is a good explanation:

http://en.wikipedia.org/wiki/Selective_color

http://www.photoshopsupport.com/tutorials/or/selective-coloring.html

http://forrestcroce.com/Articles/SelectiveColor.html

photoshop makes use of a monochrome mask layer