What a fun project. If you want, you could give your dad some "new old stock" OC filters to use and have it be maybe a central design (for example a "sun") that you could illuminate independently with a 15 watt white bulb. Then have him go to town with any colors of his wish for the outer design that you illuminate with 60 watt white bulbs.
Bill Burk, that is such a kind offer. Thanks so much. I've sent a PM your way. That is a wonderful idea to use glass made specifically for this purpose....one of those things that should have been obvious to me but I neglected. I always assumed that the old filters were simply clear glass with a colored coating of some kind (gelatin most likely). Is this untrue? Is the actual glass colored? If so then the old glass filters would be a definite source for fairly cheap and reliably safe glass to use.
I'm sorry I didn't check the post sooner. I appreciate any and all comments, but especially the couple that directly answered the question originally asked.
As far as the few folks who recommended not even trying, or to not re-invent the wheel because it might not work; I respect and thank you for the warning but at the same time am sorry that you feel so restricted. I know there are rules that must be followed but I think it's possible to follow rules without letting them totally suffocate an idea or concept. Have you ever seen a beautiful leaded-glass front door? Even with no color it's a thing of beauty. How about an abstract design? What if it were made only of ruby red and OC safelight glass? I'm not saying that the following image is what my father has in mind (we have not considered any design as of yet), but it's the type of thing I'm sure he's thinking.
I am using most of my father's old darkroom equipment and he is more than delighted that I got into the art. He is the one who brought the idea to me and I know that he would get as much joy out of making something like this and knowing that I'm using it in my darkroom as I would get using it. I will relay the relevant information to him and let him decide. And yes, when (and if) it's finished I'll definitely post a couple of photos. Again, thanks for the input.
Ooops, I don't actually have any filters. But... I know where I can get some. I'll let you know how many are available, you keep dreaming how much you might be able to use...
Ah-ha, kind of funny. I see now. Where you said "If you want, you could give" I read as "If you want, I could give". Wishful thinking on my part for sure. I'll contact the store you mentioned. Most of all, thanks for the wonderful idea.