US: Colonial Air Transport Inc. airmail labels

Here is a rare and hard to get airmail label from Colonial Air Transport Inc. Label colors in catalog listed as blue/red/white but it's uncertain. It looks like original color are like mine or it could be to different variations.

Year: 1928, Gummed. Günter Mair's catalogue no: - USA-B-8, imperforated, issued in cooperation with Western Union, dark grey-blue/grey-green/yellow, 5*****