Knowledge: The color of the mood ring changes to red, if in love, or something else but the original color is black. On the other hand, iron oxide is usually brown but converts to red, if exposed to air.

Conversation:
Red is the color of my soul. What color is your soul?
I would not know although have you heard that violet is opposite to red on the visible spectrum of light?
Never knew that actually, I've always wondered what makes the sky and sea blue though. Do you happen to know anything?
Yes, it happens due to Rayleigh scattering, which is an optical effect.
Rayleigh scattering huh? Can you go more into detail about it?
Sure, it is named after a physicist called Lord Rayleigh and is dominantly elastic scattering of electromagnetic radiation or light by particles that are a lot smaller than that radiation's wavelength.
Crazy! So much I need to learn.
Going back to red, it is due to iron oxides.
Oh, I didn't know that was red. Is that the original color or something else like black?

Response: Ah, yes. Iron oxide is usually brown but converts to red, if exposed to air.