ok, mostly makes sense.
What confuses me is the PWM outputs. There are 6 on the board I am using which would power 2 RGB LEDs (Typically). However, the configuration you mention would allow me to power 6 from the Audrino board I was going to purchase. Does that sound correct?
How can I, then, individually control all the LEDs I had mentioned (10-20)? Would I need additional PWM outputs, I assume?
And, lastly, how do I modulate the color in this scenario?
Sorry if the questions are dumb, I am just starting and this will be my first project 
I know electronics from my EE days, but it's been awhile since I have breadboarded anything.