Great Northern introduced Big Sky Blue paint in 1967. Among the locomotives delivered new w/ BSB paint were the F - 45's, U - 33 - C's, SW - 1500's, the last SD - 45's, & the SDP - 45's. Because of the short ( 3 year ) span between BSB & the Burlington Northern merger in March, 1970, only a small portion of the existing fleet was re - painted. Also due to the short time period, it was undetermined how the bright blue paint would hold up. Some rolling stock delivered new in BSB, that was not re - painted, tended to fade to a chalky, pastel blue.