The victims, a mother, her son and a friend, said they were walking towards the Rockwood MAX station at East 188th Avenue and East Burnside Street, when they were approached by three African-American males at about 8 p.m.
Dawn Swallow, who has a black eye from the attack, told KATU News that "three tall black guys crossed the road and kept saying 'you ain't black, you ain't black,' and hit us."
She was punched and knocked to the ground.
Her son, Tyler Swallow-Jones, said he went to help his mother back up when he was set upon by an attacker. He said he was hit in the head and fell to the ground.
The victims said one person did most of the attacking while the other two stood by and watched.
The attack comes after Gresham Police and MAX officials boosted the security presence on MAX trains in Gresham after a string of violent incidents, including an attack on a man by a teenager with a baseball bat.
Police say they do not have much to go on and hope someone comes forward with additional information about the incident.
No suspect information has been released.