LaserCube [0] uses additive color mixing using three primary laser diodes (RGB) aligned using dichroic mirrors (which reflect specific wavelengths while allowing others to pass through) so that they exit the aperture as a single, combined beam. Alvanometer scanners tuned to 30,000 points per second is fast enough to trick the eyes.

The complexity of the system would decrease with an anycolor laser.

The only other attempt I have seen that is similar is Seb Lee-Delisle who created a project called "Laser Tempest," which involved hacking the original code of the 1981 Atari classic to run on a high-powered RGB (white light) laser projector. By bypassing the traditional CRT monitor and sending the vector data directly to the laser's galvanometers, he was able to project the game at a massive scale onto walls, buildings, and large screens at various technology and arts festivals.

[0] https://www.laseros.com

Combining red, green and blue tricks our eyes into perceiving any color that we can perceive, but it's a very different thing to make a laser that can output any wavelength, like they do here.

The Laser Tempest sounds neat but I cannot find it, could you provide a link?