In PSP8 (Traslatable)
Uses Fills, Hue/Sat and Channel Mixer. Lots of my explaining, but that can easily be glossed over if you don't care about the whys.
Get your icon base. I've grabbed a base I made from the Taylor Swift "Love Story" video. This colouring is good for yellowish caps.
Depending on how dark your base is, you may have to do many screen layers or none at all. In my case, I did one, on 50% opacity.
My icon is very yellow, so I want to combat that with some blue. Blue = the opposite of yellow in the graphic world. I choose a medium blue colour and put it as a new layer, set on Burn (Colour Burn for PS users) @ 50% opacity.
Now that I have my colours a bit more balanced, I want to bump them up a bit. So I make a new Hue/Saturation adjustment layer and set the Master Sat to +40. You may need more or less Sat depending on how bright your picture is to start. The yellows are very unnatural looking when I do that, so I go into the yellow tab and set the Sat to -20. You may not need to do this on your icon, or you may need to do it for another colour. If there is one particular colour you think is too bright, go the tab for it and lower it a bit.
(with Yellows) (Yellows lowered)
Now that the colours are brightened up, I want to make it 'pretty'. I make a new Channel Mixer adjustment layer, and use one I've saved from a tutorial by x_robotlove @ wonderplanet. This, folks, is a miracle layer. It looks good on almost any icon and you can do tons with it in terms of how you set the blend mode.
As you can see, this bumps up the reds and cyans and mutes the yellows to give Taylor's blonde hair an almost white look to it.
This looks pretty good, so I could stop here, but I want to bump up the effect a little more, so I duplicate the Channel Mixer layer and set it at 50% opacity. You can try setting this layer on Multiply or Soft Light for a different look, too. You can really experiment with it.
I want to bump up Taylor's blue eyes a bit, so I make a new Hue/Saturation adjustment layer and up the Cyan Sat on it. Again, you can experiment with this a little, upping different Sats to highlight different colours. I set the Sat layer on Colour (L).
The whites look a little too white and boring now, I so make a new layer and fill it with a dark blue, then set it to Exclusion at 50% opacity. This gives a little pinkness to it.
This is the time to fiddle with your layer opacities if you need to to make the icon look nicer. I might up the screen or burn layer or lower one of the other layers, depending on what I want. In this case, I up the screen layer to 90% to make it a bit brighter.
I merge visible (Layers > Merge > Merge Visible) and sharpen the icon. I might smooth her skin with the Soften tool on a lower opacity. And I'm done!
A Final Word:
If you have greens in your image, they will turn Cyan with the Channel Mixer layer. If you don't want this, try setting the Mixer layer on Soft Light. It should fix the problem, though the yellows will be more prominent this way.
If you have any questions, don't hesitate to ask. Thanks for dropping by!
Joincitadel_icons for more icons and tutorials
All caps used for these icons are from Fearless.