A few B787-8 aircraft have been spotted in customer colors.
#1 is from Oct 2010, two B787-8s for Royal Air Maroc, and one in JAL colors.
#2 is B787-8 N787EX (cn 40691/2), in the colors of ANA, caught in Sept, 2010.
Nothing in the colors of a US carrier yet...
Northwest had 18 Rolls Royce powered B787-8s on order, but with the Delta merger, those aircraft will be delivered in Delta colors.
Continental also has an order placed for 8 GE powered 787-8s, as well a 17 GE powered B787-9s.
I can't wait to fly on one of these...