Clearly I’m not getting what you are saying. But tried the following based on assumption that you are using black as your background color and when we hover mouse on image it should look grey.
Hi Madan, thanks for the advice, you were right, I didn´t explain myself in a proper way. In fact, my problem was the checkered background behind the image. And that was because the png wasn´t a png but a jpg. I fell like a dumb ha ha. Thanks anyway