Very easy to do and mine look ok. Buy a tinting spray and a clear laquer, give them as many coats as you want of the tint spray to get the desired shade, let each coat dry fully before deciding, I also had a bulb rigged up to check that light would pass through in adequate quantities.
Once you have your desired shade, put a clear laquer on to protect the tint and provide a nice lustre. Make sure that the place you're working in is warm and dry too.
Make sure that you clean your lights fully, I used thinners but you must not linger too long with the stuff or it eats the plastic. If you get any runs in the paint, you'll need a fine grade of wet dry to take them out, I also use meguiars scratchx or T-cut metallic for the same job, depending on how severe I need to be.
A note of caution, if you buy from ebay, be careful, I bought mine as E marked but the dipstick had sprayed them so dark that you could've let a small neuclear bomb off inside and you wouldn't have seen the flash!! I had to strip his paint off with the thinners and start again. I don't know how much spraying you've done but it's a very easy job to do if you don't rush.
http://i17.photobucket.com/albums/b76/philskynet/SPA57292.jpg
