I choose red for this because several reasons. I want some autumn atmosphere, and this colour is very predominance on this season.
And if you are paying attention, you can see that the shadows of green are red, and the shadows of red are green. That make a whole atmospheric composition.
Here i do a bossage in the leather. just with a light colour, and do some shadows on specific areas (witch are marked by light) with a dark colour.
The trick i use to do red, is put as base colour, the red i want for the maximun light and from there, getting darker.
This way, you´ll never have pinks or oranges in the red.
Now i´ll do some nmm in the diadem and the medallion.
i use for the base colour this ocre, and for shadows, the fantastics andrea inks. For highlights, i mixed the ocre with white.
If you wanna some more advices until now, please leave me in the comments.