Nice idea, and I think Etho would love this, as he said in his last episode that he wanted some blue light in his cave.
The part with combining blue and red glass might seem a bit difficult, and problaply the biggest lag part. But, light in MC have never been very much laggy (except light issues, witch is more concidered as a bug). The blue glass would look very cool in caves.
I very much hope this will be implemented in the game, and hopefully we might get a mod at first.
For the lighting, I would love to have it, so long as it was very light on computing resources.
If there is a will there is a way especially with coding. It's not like they would be adding dynamic lights or anything, it's just a color code change. No different than if the color was purple to begin with.
This is an excellent idea. The idea is sound, the potential is enormous, and the process for creation seems fair (just as long as colored sand is a very explicitly refined, rather than natural resource).
Although, I'm not sure about the lighting dynamics described. In real life, it seems like blue light would eminate from the sides of the light source covered by blue panes, and red light would eminate from the side covered by a red pane. Rather than, as you seem to be describing, the light emination following some sort of average ratio that doesn't seem to be reflected by actual light dynamics.
Then again, I'm not an expert, and perhaps you're laying out the dynamics like that for game mechanics reasons rather than light dynamics reasons.