In the end LEDS are personal preference and as Nino and Wotto have mentioned a lot of trial and error.
I have found my likes...
![naughty &&](http://www.aussiepinball.com.au/Smileys/classic/naughty.gif)
The only 2 colours that do not do much for me are yellow and orange. They just don't pop.
AS for GI...they are great...wide angles for me are perfect. No direct beam instead a widespread hue of light.