I'm really intrigued to learn what the class will be called. I think that would have ultimately defined the colour I would choose.
But, not knowing when we'll find out, I decided to go with Red, just because I think it seems to work better with the design. Though I'm not sure whether the purple colour of the Grimoire of Time (I think a darker colour, such as grey, dark blue or even a darker purple could be better) or the blue of the leggings (which I also feel could be better grey or darker blue) fit so well.
I do wonder which parts would become colour customisable if that does turn out to be a possibility.
It's looking fantastic so far and I impatiently look forward to further updates. Great work Tomix! :D