I color the logos on the bottom of all my S&W mags -- to distinguish the M&P9 from the M&P40 mags in the mag bin. White for 9mm, Blue for .40. Doesn't look bad and helps make sure I take the right ones with me to the range. Nothing wrong with a little personalization, either wax or nail polish.
I used different colors to help match my FS M&P9 and M&P40 slides and magazines. Gold for the 9mm, silver for the .40. Just one more way to try to "error proof" by adding another visual indicator.
I do admit that I like the antique gold better, so I also used it on my Shield40 and on the lettering on my Ruger Mark III Target as well. A bunch of people at the club are also shooting Mark IIs and IIIs in competition, and this really stands out as something a little different.
