How can I remove discolouration on my ceramic dish? I have some very pale blue/grey dishes that have (what looks like) specks of grease that have "burnt on". You will see why I put that in quotation marks in the photo.

It looks like it would come off easily, or just with a bit of elbow grease and hot water, but it doesn't!

I use non-stick safe scourers, washing up liquid and hot water, as per the manufacturers instructions but can't remove.

Does anyone have any tips/tricks for how I can do this without damaging the surface?
So I wasn't sure how well it would work (since these appear to be some sort of burnt on grease stains) and it didn't get rid of everything but I think it might after a couple more careful applications.

I used astonish tea and coffee stain remover (I have no affiliation to the brand).

I figured it was the only tough stain remover I had in my cupboard that was safe on ceramic.