Most Welcome,

To change the color of add-to-basket icon you can use the below CSS code in Theme Settings >> Custom CSS >> Global Custom CSS:

body .product-list-item .woodmart-add-btn>a:before,
body .woodmart-hover-base:not(.product-in-carousel):not(.hover-width-small):not(.add-small-button) .woodmart-add-btn>a:before,
body .woodmart-hover-button .hover-mask>a:before,
body .woodmart-hover-info-alt .product-actions>a:before,
body .woodmart-hover-quick .woodmart-add-btn > a:before,
body .woodmart-hover-standard .btn-add>a:before,
body .woodmart-price-table .woodmart-plan-footer .add-to-cart-loop:before {
 color:black;
}

Best Regards.