Herb started with Compton Junior College playing two years. Singleton threw at least one touchdown in every game he played with Compton. He completed 236 of 522 passes for 3,861 yards and 33 touchdowns. In 1972, Singleton transferred to University of Texas at El-Paso where he backed up Gary Keithley becoming the first black quarterback in UTEP history. Herb quit UTEP after two games. In spring of 1973 Singleton transferred again as a Junior to University of Oregon. In his junior season, he completed 109 of 234 passes for 1,333 yards and 10 touchdowns. This passing performance was the 5th best in Oregon history at the time despite the fact that he didn't become a starter until the 5th game. Ranked 4th in PAC-8 Passing in 1973 and was named an honorable mention All-Coast by UPI. Against Washington, Singleton completed 16 of 25 passes for 224 yards and 3 touchdowns. The PAC-8 conference council deemed Singleton eligible for his senior year after debate regarding his UTEP tenure for two games. In an off-season non-football accident, Singleton broke the wrist of his throwing arm which required surgery. The injury ended his college football career.
Herb signed a contract with the expansion franchise Seattle Seahawks in 1976 becoming the first black quarterback of the Seahawks. Singleton was again found himself competing with Gary Keithley. Neither made the regular season roster.