The colour matrix is the only quick way to change a whole bitmap - but the maths of the matrix is tricky, and if the bitmap has many colours they will all be changed in strange ways.
The 'On Colour' 'Off Colour' modules in the schematic were as far as I got understanding it - they will always reliably turn black into the colour that you choose, while keeping the alpha (so transparency is not affected).
Feel free to use any schematics and algorithms I post on the forum in your own designs - a credit is appreciated (but not a requirement).
Don't stagnate, mutate to create. Without randomness and serendipity the earth would be just another barren rock.