Venetian red vs burnt sienna

Venetian red

adj

Of a brownish red colour.

noun

A brownish red colour.
A pigment producing this colour, derived from nearly pure ferric oxide (Fe₂O₃) of the hematite type.

burnt sienna

adj

Of a dark reddish brown colour, like that of roasted sienna.

noun

dark reddish brown colour, like that of roasted sienna.

How often have the words Venetian red and burnt sienna occurred in a corpus of books? (source: Google Ngram Viewer )