Paul Levitz (aka DC's President) has said to Newsarama that there are several color variations, which will be used based on a) readability due to background color, and b) mood of the product. So you might expect a DC logo on the cover of Detective Comics to be a bit more somber than the one on the cover of Johnny Bravo.
"Hi, Batman!"
"Hi, Comissioner Gordon! Huh-HAH!" (combs cowl, slaps on shades)
"This is Lt. Renee Montoya!"
"Whoa, mamma!"