There are quite a few people on this board who get their colors by building an RGB, or the cheaper RGV laser system. Many photos of the dazzling array of colors that can be produced have been posted here over time.
Ability to vary the power of the red, green, and blue or violet allows quite a variety of colors. Have you seen rog8811's 7 color handheld spirolaser? This is a lot cheaper than buying sensitive, fidgety DPSS lasers that need big pumps and huge expensive crystals to get decent power output at only one color. Also, if you like color, a multiline argon can be a good way to get several interesting wavelengths out of one laser. He Ne can be found in green, yellow, and I think orange.
Sadly, we are probably still several years of waiting away from having various green and blue diodes available to experimenters. Hopefully TV by laser projection will get us these mythical green and blue diodes eventually.