I bought my daughters two identical swiss army knives for Christmas. To tell them apart, I wanted to mark them in a permanent way. I decided to engrave the plastic with the laser to give it some relief, and then fill in the impression with acrylic paint.
The neon green paint was somewhat translucent and the dark red showed through. Had similar results with the other colors we tried. The solution was to fill the impression with a metallic silver base coat, which gave it a shiny base, and then reapply the color coat.
I used my own knife as a test case (so I wouldn’t mess up theirs), and here is how it turned out:
The font is a little jagged, especially the small flourishes. The girls opted for simpler fonts and they came out a bit cleaner.