I haven't seen RWBY or WITCH, but if you're fine with me revising the design of my character a couple times, I'll take a stab at something.

I was going to say lavender, but by the time I got home from work I was beaten to the punch. Oops.

A few questions for you:

What's a flowerpot character? My best guess is that it's a fragile or helpless character who won't grow without intervention from other players, but I'd like to be sure.

What's the relation between spells and sub-spells? Are spells a category (like ice), and sub-spells are the specific attacking moves?

Actually, I'll read anything you have for how magic works in your setting, even if it's long.

I'm on Discord pretty much all the time, so a server would help me out a lot!