1- Take your cap and crop it to your liking. I used one found here of Raito from Death Note. :D

2- Duplicate your base and set it to Screen 60%. You may skip this step because not all images are dark.



3- Layer -> New Adjustment Layer -> Selective Coloring

Neutrals
C: -14
M: +17
Y: +30
B: -2

Blacks
C: +13
M: +12
Y: +15
B: +12



4- Add another Selective Coloring layer with these settings

Reds
C: -57
M: 0
Y: -28
B: 0

Yellows
C: -22
M: +14
Y: -6
B: 0



5- Now go to Layer -> New Adjustment Layer -> Curves

RGB
Input 1: 49 Output 1: 57
Input 2: 182 Output 2: 186

Red
Input: 172 Output: 175

Green
Input: 174 Output: 172

Blue
Input 1: 61 Output 1: 55
Input 2: 157 Output 2: 160




6- Layer -> New Adjustment Layer -> Brightness/Contrast

Brightness: +5
Contrast: +5



7- Layer -> New Adjustment Layer -> Channel Mixer

Red
100
-4
+1

Green
+2
100
-1

Blue
+4
+4
100



And voila! We're done. Remember that this might not work with all images so play with the settings until you get the result you want! ^__^ 

Other icons made with this tut: