Delta Airlines and their Delta Connection partners have rich history of special colors. The mainline fleet has sported schemes from Olympic special colors, promotional colors, anniversary colors and, more recently, SkyTeam Alliance colors.
The Connection partners also have had various special colors that included Olympic colors, regional specials colors, etc.
Most recently, some Delta jets have started showing up with Signatures of various important individuals on the nose.
Hopefully we will keep seeing more Delta special schemes more often!