The phrase "black splotches" refers to dark, irregular marks or spots that appear on something, usually creating a contrast against a lighter background. Full definition
Tibbetts found that a lot of fighting is not necessary, however, because the wasps signal their strength and status with the number of black splotches on their bright yellow faces (more splotches denote higher status). (discovermagazine.com)
She had an adorable face, with black splotches framing her eyes like clown makeup, but she was randomly aggressive toward men and other dogs. (animalsheltering.org)
It is generally dark, with purplish black splotches on a dirty white background. (AmbergrisCaye.com)