I just received a swatch book of colored filters and diffusion film from Rosco (Roscolux Swatch). I'm ordering another swatch from Lee Filters and I'll post a link to them (Lee):
http://www.shop.leefiltersusa.com/LEE-Swatch-Books_c4.htm
If you use the coupon code "swatch" during checkout you will only be charged a penny plus shipping ($5 approx).
The filters are roughly 3 " by 1 3/4 " and there looks to be about 50 or more filters. They are fun to experiment with and you can use them in front of or behind the lens of your flashlights. If you have a LED tint that isn't to your liking you can shine your light through these filters until you find one that makes your light more pleasing to you. You could also use them over a camera's flash if you wanted.
You would then just cut a circle out of that filter. These would work only on lights from P60 sized on down.
The colored filters (as opposed to the diffusion filters) have some information provided for each filter as well such as % of light transmission and a spectral curve showing how much of each color range is transmitted.
Or you can just shine a light through them and see which one you like :)
I'm describing the swatch from Roscolux as that's what I just received but I think it's similar for Lee as that's what I've just ordered.