EXP: YCN - The Witches Research

I am also very tempted to illustrate a scene from the Witches for YCN. I've done some research into what already exists regarding the witches, just because I'm not really sure what colour palette direction to go in (and thats one of the main things I wanted to focus on for this).
Now I know that gouache is the way I'm going to make these I really need to nail down the colours first.

When I think of the Grand High Witch, I think regal colours red and purple. She is elegant but also very scary! As I'm aiming my illustrations at children, I don't want them to look anything like the movie version because that was straight up messed up and gave me nightmares as a kid. 

I liked the scene in the hall the best with all of the witches cheering her on so that's probably going to be the scene I choose. With this brief it asked for One Fantastical Creature, One child hero and one villain, so that means that this illustration could equate to being the fantastical creature (witch) or the one villain (grand high witch). As I already have Fantastic Mr Fox, I'm not sure whether he counts as the fantastical creature (probably) so that free's up the Grand High Witch to be the villain and Matilda to be the child hero. 

Im going to start with some sketches so I can really nail what I want her to look like, grand but scary!