Knowledge: The first color in the rainbow is red while, for the visible spectrum of light, it is purple.

Conversation:
I really enjoy the color red. It can denote passion and love. What is your favorite color?
No favorites here. Have you heard of a visible spectrum of light? Red is the color at the end of it.
I have not but that's pretty interesting to know. Do you know the first color then?

Response: Oh yeah, the first color of the visible spectrum of light is purple.