I'm looking at putting a M500B on a Bushmaster M4.  The rifle will be used primarily as a patrol rifle in mid-range applications (perimeter control).  

My question is that I know alot of the new lights come with navigations lights.  I wondering if anyone has any input on pro/cons of the different colors.  I've always been told that red is better for maintaining a person's night vision, but figured I would get everyone's input before I drop $400-500 bucks.
I think the options are white, blue, and red.  

Thanks in advance.

I have used the white on a primarily entry weapon and loved them.

Same here....I would have probably gotten the blue nav lights, but they weren't available when I bought my light. I have been very satisfied with the white lights.....