We learn that pea soup green is Egon's favorite color, and Ray has a tuxedo in that color. Which is why Ray is "such a lonely man," Peter says.
Peter: Is there anything in your combined genius that could have made this car...pretty?
Ray: This is beautiful!
Egon: (deadpan) Yes, I'm very excited about it.
Winston: I don't believe it, the thing just keeps getting uglier!
Egon: Nobody said that science was pretty, Winston.
Peter: If we play our cards right, we could meet the Queen of Soul!
This is referencing Aretha Franklin, a Motown recording artist, who is considered the "Queen of Soul". Her name is not spoken in the episode, however.