Well, here is a photo of the BOAC livery on a Concorde; pretty sure it never actually was painted in those colours.

http://www.boacvirtual.fsnet.co.uk/

It also flew in Singapore Airlines colours down one side in joint BA service, the Pepsi promotional colours, and Braniff did several mockups as well for its jointly operated Washington-Dallas service, never actually painted up, which can be seen below:

http://www.braniffpages.com/concorde.html