1
general::
An exclamation of enthusiasm or encouragement, as in You've said it really well? right on! This interjection has a disputed origin. Some believe it comes from African-American slang (it was recorded in Odum and Johnson's The Negro and His Songs, 1925); others feel it is a shortening of right on target, used by military airmen, or right on cue, theatrical slang for saying the right lines at the right time. [Slang; first half of 1900s] Also see WAY TO GO.
American Heritage Idioms
2
general::
Phrase(s): Right on!
Sl. Exactly!; That is exactly right! • After the speaker finished, many people in the audience shouted, "Right on!" • One member of the crowd called out, "Right on!"
McGrawhill's American Idioms And Phrasal Verbs