I don't remember exactly what he said, but it was about how it used to be difficult to make blue paint and that Leonardo da Vinci and other painters used to grind lapis lazuli and mix the powder with egg yolk and white wine to get a deep blue color.

He then did these steps but didn't get a deep blue color, which he said was because he hadn't gone through the arduous process of grinding and filtering only the bits from the rock with the deepest color, and that this long and arduous process was what made it so expensive in the past.

I suppose my dream was half true since Ultramarine was a really expensive paint made out lapis lazuli. ~~Though I still have no idea why I dreamed about a Vsauce short of all things.~~