David Cook tutorial
from
to
-using Selective Coloring and Hue/Saturation
-only three steps, pretty easy (it has to be easy if I made it, lol)
Before you begin, crop your base (and sharpen it if you want to. I don't usually).
Duplicate your base, set it to Color Dodge and lower the opacity until the icon looks normal. For this example, I set it to 42%. It makes the image look softer.
Go to Layer --> New Adjustment Layer --> Hue/Saturation, Edit: Master. Under Saturation, I moved the arrow-thing around until it brought out the reds in David's beard without overwhelming the icon; +36. Then (in the same action) in the Lightness box-thing, I put -18 because I liked how it made the icon grayer.
And lastly, make a Selective Coloring layer (Layer --> New Adjustment Layer --> Selective Coloring). I put in these:
Reds: -88, 0, 33, 0 (to bring out the reds some more)
Whites: 57, 0, 0, 0 (to make the image even more gray)
And that's it! :) I hope this helps!
Other examples:
and
(please excuse the bad cropping on the Luna example, it's just an example of the coloring. :P)