Pure color has more power next to gorgeous grays. Just Look at Turner's work and you will see. He didn't use dark foils to make luminosity. Sanford Gifford didn't use darks either. Instead there is one pure point and the rest is grayed.
at the NGA, Siout, Egypt, Sanford Gifford
at the Met, A Gorge in the Mountains, Sanford Gifford
Here are two I have visited recently. Aren't they exquisite?