I’ve been looking at this as the site I’m developing for a client has the exact same problem.
If you are using one of the custom colour style sheets then they override wp-content/themes/mystile/css/layout.css.
Check in wp-content/themes/mystile/styles and the relevant colour css sheet is in there. Its on line 4150 or Paragraph 7 – Woocommerce /* 7.2.1 Single Product */