Lets you to build red, green and blue colored lights. Requires very quick research.
Download
http://ludeon.com/forums/index.php?action=dlattach;topic=2614.0;attach=1476
Install
Extract in the Rimworld Mods folder
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I wouldn't normally say anything, but I kinda already did this, and mine has the coloured sun lamps too :/
http://ludeon.com/forums/index.php?topic=2287.0
Sorry did not realise. :(