Coloring (Painting) Vex Component to be identified by Color Sensor

The team I am trying to help wants to color(paint) some of the Vex Components. (They plan to color them using Acrylic paint) so that they can be identified by the color sensor.
Is this legal - or it will be against rule R13

Sounds like that is serving a function, and would not be legal. I would post in the official q and a for further clarification.