$25,000 Pyramid, episode #607, airdate January 15, 1985.
Ed was wearing a vivid green shirt and made a self-deprecating joke about how they were going to chroma key an ocean background onto him. Dick responded that he didn't know what "chroma key" meant (my guess is Dick DID know and feigned ignorance to make the moment a little more audience-relatable).
At the end of the show, after Ed's explanation of chroma keying, they did a little experiment and found that Ed's green shirt was just right for a chroma key effect, so they superimposed Heidi Bohay's body underneath's Ed's head & neck.