This is a poorly designed but very useful gridfinity print for storing and stacking the two thin coats line of paint. Since it uses three shades for every color, you can store like colors together in a way that is easy to identify on the fly. No more deciding shadow colors by eye after a few beers. 

Space around the bottles is about 24mm, which is too small for normal paint bottles. But the two thin coats line is a very unique shape. There is extra room for even the sausagiest of fingers to easily excavate. 

Onshape Cad