Not sure about the 18'U. I only have notes on the 22'. If it has a blue bottom and blue upholstery like the 22' it would stand to reason it could have been blue. Aside from that, black was the default.
1924 Hackercraft 33' Runabout 'Miss Dearborn II'
1938 Gar Wood 22' Streamliner 'Empress'
1954 Chris~Craft 19' Racing Runabout #498 'Nervous'
customer boats in the shop:
1941 Chris~Craft 19' Barrelback #48873
1947 Chris~Craft 25' Sportsman Sedan #075