Lasersensitive pigments
Even plastics which normally don't take well to being laser-labelled can be provided with a contrast-rich marking by using laser additives.

Laser batches are specially designed for the desired colour shift (light-to-dark) and the type of laser used.
Anti-Static Agents
Adding an anti-static agent to the master batch or plastic prevents this effect.
UV Protection
High-energy UV radiation has a negative effect on plastic and the product as a whole.