"There are many additives you can put in polymers (either in pellet form, or loose along with the pellets as you're processing) to achieve this visual appearance. The additive to use would vary depending on your polymer, the process you're using and the processing conditions. My company specializes in these types of additives, but to me these pictures look like the effect is painted on rather than molded into the part. Maybe it's just the picture though, as paint or coating for a breathalyzer application would surely be problematic with use & cleaning."