My idea is that stained glass would tint blocks with the light that passes trough them. (eksample: a glowstone behind a red stained glass would make a red tint on the room it lights up)
Don't know how hard it would be to make it, but think it would look pretty awesome.
Hi there. Your idea has been to an extent already been sorted by the Albedo Mod.
Albedo basically allows other mods to add coloured lights to the world and I dont mean coloured by the block is red and the light is white, I mean that the white is tinted red.
To use albedo though, you will have to find other mods that uses albedo for coloured lights.
Hope this helps.
There are albedo addons for vanilla stuff.