I'm toying with the idea too and have been told either go with green or red, but definitely not white.
We have been advised to avoid adding lights that are not USCG approved as NAV lights...especially if they are RED or GREEN and also to not put blue colored lights where they may be at times underwater. http://www.uscg.mil/hq/cg5/cg545/alerts/1015.pdf
Such an equipped boat (illegal added RED lights) recently caused very unnecessary safety risks on Lake Austin as it was appearing to be on a different heading that it actually was. The confusion was causing oncoming boaters with the actual safe right of way to instead change course and steer into its fast moving path.