No and if yours does you need to take it to the vet it might have an infection
If you have brown spots on the roof of your mouth, it could be patches of melanin. Another reason brown spots might show up is because someone smokes.
Cats (and dogs) often have black markings in their mouths and on the insides of their lips that are just normal colorations. This is often the case with cats with multiple colors of fur. Unless it is sore or causing pain for a cat it usually is not a problem.
If the spots are only thru the clear coat the entire roof should be carefully finesse sanded and then reapply clear coat as directed by manufacture.
Strearks on roof
Because white reflects heat whilst black absorbs it therefore a white roof will keep the house cooler as the suns rays will bounce back off of it whereas a black roof will absorb the suns rays.
The black-colored roof absorbs more sunlight and heat compared to the white shiny roof, which reflects more sunlight. This absorption of heat causes the black roof to become hotter than the white shiny roof.
Probably
To determine if your roof is leaking, look for water stains on the ceiling, walls, or attic. Check for damp or moldy spots, peeling paint, or sagging areas on the roof. Inspect the roof for missing or damaged shingles, cracked flashing, or clogged gutters. If you notice any of these signs, it's likely that your roof is leaking.
Roof wetting is a Bermuda custom. The participants climb to the roof anda bottle of black rum is either poured on the roof or is shared, or both.
Water spots on the ceiling could be caused by condensation, plumbing issues within the walls, or a roof leak that is not directly above the spot.
It is normal for some dogs to have a black roof to their mouth; it is simply part of their natural colouration. If the black part looks lumpy or is growing oddly then you should take your dog to the vet.
Sun damage.