This is a lovely word, with a fine flowing cadence, but it’s all too rare, surviving only in poetic or elevated writing. As an adjective, it refers to a blood-red or crimson colour; as a verb it means to render something that colour. However, it’s recorded in English in the sixteenth century in the sense of a pale pink colour, having been borrowed from Italian incarnatino, derived in turn from the Latin incarnato, something incarnate, made flesh.
(Our name for the flower called the carnation, comes from a related idea, as its flowers were originally the pink of European flesh; its name comes from the related late Latin word carnatio. Both it and incarnato derive from the Latin caro for flesh or meat, as do other words in English, such as carnal and carnivorous).
But if we know the word, it probably reminds us of Shakespeare’s Macbeth:
Will all great Neptune’s ocean wash this blood
Clean from my hand? No; this my hand will rather
The multitudinous seas incarnadine,
Making the green one red.
As a result of that image, the word shifted sense to mean not the pink of flesh but the red of blood.
We have other words in English for the colour, such as crimson and carmine, so it’s not surprising that incarnadine — whether as adjective or as Shakespeare’s verb — has survived only in a limited way, usually in contexts that suggest associations with blood. Thomas Hardy used it in Far from the Madding Crowd: “Repose had again incarnadined her cheeks”. And this appeared in the Independent on Sunday in 1995: “Barbadian fishermen rushed into the bay and began clubbing the dolphins to death ... Within minutes, many of the trusting mammals were dead and the turquoise of Miami Bay was incarnadined”.