The Arbiter of the Gods
I seriously wouldn't worry. People - especially noblemen - of the 15th century wore bright clothes. It was a sign of status. And if we can assume that coffee, tea, silks and spices are being imported I think it's a very safe bet to say that dyes are common too.For context I'm relating it to the colour of the Emberlark feathers and it would have to be a rather bright orange/red colour, I'm not sure how close you could even go.