I'm looking for about 200 LEDs (high brighness, ~8000mcd) of each colour in red, blue and green. I'm wondering where I could get these reasonably cheap. I understand you can usually get great deals on cheap Chinese trashy LEDs - they don't need to be perfect, I will be able to replace them if they burn out and they will be slightly diffused.
https://www.futurlec.com It takes about 2 weeks to get stuff shipped to the US from them. They have tricolored LEDs there too, if you would like the RGB all in one bulb.
All of those are ok, but a lot of their ultrabright LEDs range at almost a dollar an LED (All Electronic's Ultra Blue is $1.75 each!).
If I'm buying 200 of each this will be very expensive! There is www.besthongkong.com has the best deal so far, I don't really mind if they are not as good quality as I can easily replace them, etc.
Having specs on them is very important. If you get a batch on eBay and run over their rated current because they didn't give it to you, they lose output permanently and may burn out. Not just one, they'll all degrade together.
Note that this is buttloads of assembly work. Thus you don't want to screw it up.
Also when you work in the assembly issues, you may find it cheaper to go with a higher powered device. Superflux LEDs are much more powerful than normal LEDs, and a Lamina Light Engine ($10-$20) has the power of buttloads of LEDs.