So basically you need to have a different material in blender with the colours you want. Have the colour seleced in the materials menu then go into the (materials and ramps or something like that) menu, the one with the colour prview with the ball. Look for a part that says something along the lines of Material.001, and rename it to something like blue. Then, in the .zip for the addon, have a 16x16 (preferably, I dunno if it makes a difference) blue.png file. You'll need to do this for all the different colours.