Hello,
Try to add the next code in Theme Options > Theme custom CSS:
.st-swatch-preview li.sten-li-disabled span:before { background: linear-gradient(to top left, rgba(0, 0, 0, 0) 0%, rgba(0, 0, 0, 0) calc(50% - 0.8px), #222 50%, rgba(0, 0, 0, 0) calc(50% + 0.8px), rgba(0, 0, 0, 0) 100%); } .st-swatch-preview li.sten-li-disabled { border-color: #222 !important; }
Change #222 to the desired color.
Regards
