Using the beautiful Model, Mona Johannesson, I'll show you how to do yellow/magenta coloring using only Selective Color. The Image I've used here and more can be found at
MonaJ.net.
Remember-- Tutorials are supposed to show you the possibilities of your program. You can copy the steps exactly as they are when you make your own but you'll learn more by customizing each one as you go to suit your taste.
Before -> After
X] Beginning with the base, cut, copy, crop as you please.
X] Copy base and set layer to Screen at 35% opacity, or however you like.
X] Go to Layer --> New Adjustment Layer --> Selective Color and type in these settings:
Reds
Cyan: -100%
Magenta: +100%
Yellow: +100%
Black: +44%
Yellows
Cyan: -100%
Magenta: 0%
Yellow: +100%
Black: 0%
Neutrals
Cyan: 0%
Magenta: -14%
Yellow: 0%
Black: 0%
X] Then make another Selective Color Adjustment Layer and type in these settings:
Reds
Cyan: -49%
Magenta: 0%
Yellow: 0%
Black: 0%
Yellows
Cyan: 0%
Magenta: 0%
Yellow: +21%
Black: 0%
Whites
Cyan: +1%
Magenta: -67%
Yellow: +62%
Black: +48%
Neutrals
Cyan: +23%
Magenta: 0%
Yellow: -33%
Black: 0%
And you're done.
Go make sundaes.