Why the roof of my mouth looks greyish? Its always been like that I thought it was oral cancer im 22 but don't drink or smoke
Likely normal. Any coloration of the skin (or mucosa, in your case) that does not change over time is most likely normal for you. Nevertheless, any time you notice any new areas of pigmentation or changes in coloration you should discuss this with your physician. You might also ask you dentist to look at this.
Best to be. Seen by your dentist to make sure there is no problem. The mouth is dark inside so without proper illumination it might have a different appearance. But best to be checked out.