VansCheckered Ward. mens Sneaker

Sizing question: trying to order for a women's size 8.5 foot. should i get 7 d (used size conversion chart), 7 b, or is the 8.5 b already in women's?

The picture looks like a dark blue denim. Are these black canvas/twill?

should i buy 7 1/2 or 8? my son wears both sizes.

why i got the wrong size shoe