Polygala vulgaris has white, red, and blue flowers in Faroe, England, and I think Herbert says in Zante.
"More Letters of Charles Darwin" by Charles Darwin
Faroe Islands, Polygala vulgaris of.
"More Letters of Charles Darwin Volume II" by Charles Darwin
This occurs in our common milkwort (Polygala vulgaris).
"Darwinism (1889)" by Alfred Russel Wallace