Ecommerce – Effectively display sale on a product swatch

Is there an effective way of displaying a sale on a product swatch which is universally recognizable?

I have read the following NN article, which suggests icon and color are the best way of displaying this on a product grid such as a listing page. https://www.nngroup.com/articles/visual-indicators-differentiators/

My initial thoughts were a percentage symbol within a circle, but my concern is this is too obtrusive?

Any thoughts much appreciated.