Here is the code behind my Unity 2D pixel shield builder.
The core principle of this process is found in the SpriteColourModifier.cs script, where a "template" black and white pattern is used as a reference for where pixels should be drawn on the correspondingly sized sprite that you wish to change. The different shades of the black and white correspond to the new colours in the ColourSet.
All art for this project is done by Bryce Watson (ArkanPixel).