The vast majority were color-on-color. In fact, it's how ND developed the green jersey tradition -- they were ND's alternate uniform when playing dark-jerseyed opponents like Army and Navy.
White road jerseys became much more prevalent beginning in the 1950s. ND actually wore white at home once, in the 1955 opener versus SMU.
By the 1970s, it was relatively unusual, but hardly unheard of, for teams like Tennessee and UCLA with light-colored home jerseys to wear them on the road -- or, alternatively, for the visiting teams to wear their "home" jerseys at UT and UCLA. (ND did wear white at Tennessee in 1979.) I think Georgia Tech wore gold jerseys and white helmets at ND in 1970.
In 1983, the NCAA implemented a kill-joy rule requiring the visiting team to wear white and the home team to wear colored jerseys in every game. Teams like Georgia Tech and LSU, which traditionally had worn white at home, had to switch to blue or gold and purple, respectively. In 1997, the NCAA relaxed the rule and allowed the home team to wear white, but only if the visiting team consented. In 2010, after UCLA and USC had skirted the rules by agreeing to wear light blue and cardinal in their rivalry game (as had been tradition through 1982), the NCAA passed the current rule allowing both teams to wear colored jerseys if both consent and if the colors sufficiently contrast.