These are used to match up textures when you are creating your own texture map. If you're doing a texture map that mostly one colour (like skin), they're not much use. But if you are doing painted on clothing, or tattoos, or garments with stripes, they are indispensible. The colours match front to back on the template. So, if you paint a red stripe up the back of the body to one of the coloured blocks, if you then paint down the front of the body using the matching coloured block as a starting point the stripe will match front to back without any seams. Hope this helps Paul