We've had several lively threads on this in the past. I tried blue, which actually has the tactical advantage to defeat some night vision devises. I've observed it is virtually invisible under natural moonlight. Of course, the persons using the things were visible in the same moonlight to a carefull observer <img src="images/graemlins/blush.gif" alt="" /> I personally now use red when preserving night vision is a consideration. Don't forget the trick of closing one eye if you absolutely must use white.