Talk to Dermatologist on Dull Skin

Please tag a dermatologist .

I used to wear a sun block which used to look fine after applying but by the time i have realized it has started making my color look dull . I dont wear make up i.e foundations or compacts or any other thing except the sun block. Please recommend any medicated sunblock that does not affect the skin tone and is generally a good skin protector too. I have a combination skin.

Will be highly thankful.