To make something purple in color or to cover with purple.
From the prefix 'em-' meaning 'to put into or onto' combined with 'purple,' the color. This verb formation became established in English by the 16th century when writers wanted a more literary way to describe things turning purple.
Shakespeare and other Renaissance writers loved 'empurple' because it sounds more poetic and dramatic than just saying 'turned purple'—adding the 'em-' prefix makes the action feel more intense and meaningful, which is why you'll see it in flowery descriptions of sunsets or nobility.
Complete word intelligence in one call. Free tier — 50 lookups/day.