Seconding ILDA. It's been the standard for decades and it is well documented and easy to interface with either at the software/library level, or even at the signal level. [1]

You can get a cheap "RGB" laser projector on eBay for ~200 [2]. It will have red, green, and blue lasers, and the interface will be willing to combine them 7 ways. A more expensive laser will have "analog" mixing for closer to true RGB. It will also likely have no documentation, and might be weird. I have one of these.

For something with better documentation, supported API, and lots of active development, check out Lasercube [3]. It has WiFi, a documented API, a Github repo with a client, and the base software is also really cool. This is my next planned upgrade.

Be careful: Most of these lasers put out 500+ mW and will instantly destroy your eyes if you make a mistake and stop scanning. It's not an exaggeration. Find out what wavelengths your laser outputs and get certified glasses to wear when working on it.

[1]: https://www.ilda.com/resources/StandardsDocs/ILDA_ISP99_rev0...

[2]: https://www.ebay.com/sch/i.html?_from=R40&_nkw=ilda+rgb&_sac...

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