Glass reflects all visible light depending on how it catches it. But, can glass be laser cut to a specific angle, or treated, to reflect a specific wavelength of light e.g. red ?

Similar to annealing stainless steel (heating it to create an oxide layer) which gives steel "colour".

https://en.wikipedia.org/wiki/Dichroic_filter

4 hours ago, Erina said:

Glass reflects all visible light depending on how it catches it

No, it reflects a small fraction and transmits most of it.

https://en.wikipedia.org/wiki/Fresnel_equations#/media/File:Fresnel_power_air-to-glass.svg

Paint ?

Also gratings, and so on.