Hi, welcome!

Usually if I'm not sure how something would look I would look at references. Perhaps seeing other images for "Sword Saint" or "Kensei" can give you ideas of how you might want the design to look (especially if there is some historical background).

In terms of just colors, so far you have white and red. Black sounds like it could be good accent color since it's also on the eyes of the mask. Perhaps just white so it stands out against the red cape?

Perhaps this is nitpicking on the terminology, but if you are doing a design, would it be better to make something like a reference sheet first where it's just a standing pose with a front and side view so it's more obvious what you want things to look like? Then you could do a sprite of the character in a pose. Just wondering.

Hope that's helpful!