Marlin can verify, but Sunflower Yellow was indeed one of the new "spring colors" introduced within the second batch of 50 Deuces... Hugger Orange and Citrus Green were also added at this time. 10 of each were built. These 3 new colors replaced Gobi Beige, Cortez Silver, and Forest Green... Those 3 colors were only offered in the original batch of Deuces. Cranberry Red and Fathom Blue carried into the second batch with an additional 10 cars of each color being built along with the 3 new spring colors.
Our own Schoney has a Sunflower yellow Deuce he bought brand new in 70 from Rapids Chevrolet, and is one of the nicest unrestored Deuces out there. He had it at SCR2.