Splotch (noun)

An irregularly shaped spot or blot of color on a surface.

Origin:

Of uncertain origin, first recorded in the mid-19th century.

Examples:

1. The painting was marred by a few splotches of red paint.
2. A splotch of ketchup stained the front of his shirt.
3. The photograph was ruined by a large splotch of dust on the lens.
4. The walls were covered in splotches of mold.
5. The canvas was covered in bright splotches of paint.