In this small screenshot, the three navy tiles are normal but the one in the top right is showing this strange behaviour - it should be the same color.
The tile in the top right looks like either it’s a Tile Object rather than a regular tile in a tile layer, or has an object (specifically a Tile Object) on top of it.
If you’re not placing it yourself, maybe your Automapping is doing it?
If it’s not that, I’m afraid you’ll have to share your map file, as diguring things out from screenshots is often difficult or impossible.
These are collision objects on the tile in your tileset, presumably added via the Tile Collision Editor. You can toggle whether these collisions are previewed in the map via View > Show Tile Collision Shapes.