...Not in the sense of Colorizing, but in the sense of making a colored image prettier colors.
This is what happens when I get too bored. xD
I made mine in PSPX2, but as long as your program has Color Balance and Channel Mixer, you should be able to follow it.
This coloring technique brings out the reds and blues in your images.
Quote:
I’ll be using a cap of Jack and Ianto from the Torchwood episode “From Out Of The Rain”. I’ll be making an icon, because that way I don’t have to worry about blending other images in to make it pretty. 
1. Prepare your base. I duplicated mine 4 times. The first three I set to Screen 100%, and the fourth I set to Soft Light 100%. You can play around with this, because all screencaps are different.
2. Their skin is too red. I made a new Adjustment Layer > Color Balance.
Midtones: -73, 0, -19. Check the ‘Preserve Luminance’ box.
3. Now for some Channel Mixer fun. Layers > New Adjustment Layer > Channel Mixer.
Red: 173, -101, 15
Green: 8, 96, 8
Blue: -157, 184, 137
4. You could stop here, but I’m going to add a few more layers. Duplicate the base, bring it to the top, and set to Luminance (Legacy) 31%.
5. I added a new Raster Layer, and set it to Lighten 100%. Then I took a regular soft edged brush, and made a dot in the corner with a dark red.
Finished product -
1. Prepare your base. I duplicated mine 4 times. The first three I set to Screen 100%, and the fourth I set to Soft Light 100%. You can play around with this, because all screencaps are different.
2. Their skin is too red. I made a new Adjustment Layer > Color Balance.
Midtones: -73, 0, -19. Check the ‘Preserve Luminance’ box.
3. Now for some Channel Mixer fun. Layers > New Adjustment Layer > Channel Mixer.
Red: 173, -101, 15
Green: 8, 96, 8
Blue: -157, 184, 137
4. You could stop here, but I’m going to add a few more layers. Duplicate the base, bring it to the top, and set to Luminance (Legacy) 31%.
5. I added a new Raster Layer, and set it to Lighten 100%. Then I took a regular soft edged brush, and made a dot in the corner with a dark red.
Finished product -
You can add text or do whatever else you want to do to yours, but that’s all I did for mine.
Cheers, and happy icon-making!