From Technic Wiki
The Laser Focus is an optional piece of the Laser Drill assembly. You can install up to six of them in a Laser Drill; different colored foci have a greater chance to obtain a certain type of ore. For example, the Laser Focus (Black) has an increased chance to generate Coal. There are 16 different colors of which you can craft a Laser Focus, simply swap out the center Stained Glass Pane color for the one you want to craft.
Laser Focus Colors