Involves selective coloring
Using photoshop CS (but it should works with all the photoshop versions)




Rules
- don't claim it as your own
- credit isn't necessary but if someone ask you for this coloring you have to point to this tutorial
- comments are really appreciated
- if you have any questions feel free to ask
- do you like what you see? Friend me!

Let's start!

=> Remember that every picture is different so play always with the setting to fit your icon!

Step 1
Take your base and do whatever you want: crop it, sharpen it, screen or multiplay if it needs.
I chose a beautiful picture of Kristen Stewart and I cropped it


Step 2
Layers > New > Level
Fill it with a dark blue (I used #02021b) and set to Exclusion at 100%

Step 3
Layers > New > Level
Select the gradient tool and pick a light blue for the first square (I used #27b8e4) and then a pale yellow for the background square (I used #fdf352)
Screenshot in case you're confused ;)
Then click on the image, drag the arrow and release it: you should have the yellow on the lower part of image and the blue on the top --> Screenshot
If you don't know how to make a gradient, also after my terrible explanation XD, here there is an amazing step by step tutorial!
Then, set the layer to Overlay at 50%



Step 4
Layers > New Adjustment Layer > Selective Coloring, set at 100%
REDS: +30 | +81 | +43 | +42
YELLOWS: +52 | 0 | 0 | +15
CYANS: +100 | 0 | 0 | 0
MAGENTAS: +23 | +100 | 0 | 0
WHITES: +17 | +9 | +9 | -3
NEUTRALS: +13 | +40 | +7 | 0
BLACKS: 0| 0 | 0| +50



Step 5
Layers > New Adjustment Layer > Hue/Saturation
CYAN Saturation +40

Step 6
Time for add some colors!
Layers > New > Level (make a new layer for every color listed here)
--> Fill layer with violet (I used #8f0d84) and set to Soft Light at 40%
--> Fill layer with a dark blue (I used #02021b) and set to Exclusion at 100%, duplicate this level and set to 50%
--> Fill layer with a really pale yellow (I used #f8ffc9) and set to Color Burn at 40%
--> Fill layer with a soft pink (I used #ffd6c9) and set to Multiply at 30%

At these point you should have 5 solid colours layer, like this



Step 7
Layers > New Adjustment Layer > Levels
RGB channel (input) 10 | 1,15 | 250

Step 8
Add another 2 solid colours layers
--> Fill layer with a bright blue (I used #b8fffc) and set to Soft Light at 30%
--> Fill layer with a dark blue (I used #060d40) and set to Exclusion at 40%



Step 9
Layers > New Adjustment Layer > Selective Coloring, set at 100%
NEUTRALS: +6 | +4 | -8 | -6
BLACKS: 0| 0 | 0| +10



Final touch: add some brushes, text and texture, use creativity!
And we have finished!

Final Result