There are several synonyms for the phrase "black hands," which could refer to hands that are literally stained or dirty, or it could metaphorically indicate someone who has done something wrong. Some synonyms for "black hands" include grimy hands, soiled hands, stained hands, sullied hands, tar-stained hands, tarry hands, and filthy palms. Likewise, you could also use phrases like tainted digits or polluted palms to describe hands that have been marked by grease, ink, or dirt. Alternatively, if you're using "black hands" to infer guilt, you could consider synonyms like bloodstained mitts, suspect palms, or tarnished fingers.