The design is very simple/ clean and to the point. #3 works for me because the tabs makes more sense and the layout.
It clearly shows me that I am in the "Color" section and right on the top I can see the tools and options.
One thing I would do is to repeat the add to cart on top and bottom as well. If not make the CTA and price much bigger. Maybe 2x more. The font all over won't work. It's not friendly. It's not readable and not web friendly.