A recolor consists of two parts: textures and alphas. So Alphas are a part of a recoloring.
Unless Marvine specifically stated not to do any alpha edits, then you're not breaching her policy.
would I be allowed to submit the clothing to this and other sites? I know I have to give a link to the mesh here and credit to Marvine.
Yes, that's part of Marvine's policy. No paysites though. It's in the READ ME file.