I want to use different color LED's for this kit - where is the best place to buy them?

Super Bright LEDS has a good selection and they have a nice selection chart so you can compare all the spec's. We recommend a 30 degree viewing angle for rockets.

I want to use a LED that requires more than 3v, what should I do?

We can supply battery holders for two coin cells on request - this will give you a 6v supply voltage. We can also supply extra CR2032 lithium coin cells at a fair price.