Add to cart button change text to white?

I hope you have using cache plugin

Just try after flush cache

If you have a custom CSS area, place the code below into that. Otherwise put it into your style.css file of a child theme:

.single_add_to_cart_button {
  color: #fff !important;
}

Cache is cleared just need to try change the text colour on the Woocommerce single_add_to_cart_button

.product-summary-wrap .single_add_to_cart_button {
  margin-top: 0 !important;
  color: #FFF !important;
}

Try this code and check after clear cache

Thank you ??