I used a normal MDF board for layer 1 and previously painted it with black acrylic paint. Of course you can also use black MDF boards. 
The engraving of layer 2 only serves as a support in order to be able to accurately place the individual parts from layer 3 that are to be cut again.
 

I painted the parts from layer 3 with the appropriate acrylic paint (white, red, green, yellow) as in the title picture.

After the paint has dried, the parts from layer 3 are glued to the areas marked with the engraving.