The color of the outpout is measured in nm. 532 is green, 442 blue, 405 violet, 650 red. Anything above 750nm or bellow 400nm is invisble (infra-red and UV). Power is measured in Watts. 1mW is 1miliwatt, or 1/1000 of a watt. So, 50 mW is 10X brighter than 5. Also, the eye is able to see some colors of the spectrum better then the other. Green is one of the best. For a graph, se here, at the top of the page. http://www.laserpointerforums.com/forums/YaBB.pl?num=1217284580