Of course plenty of schools use gold but their other color is not white. That's the problem - white and gold do not contrast enough, necessitating a third, darker color i.e. navy.
Colorado for instance - their official colors are silver and gold, but they wear black and gold because it looked like ****:
The official colors of CU are silver and gold. According to the book Glory Colorado, these colors were adopted by the class of 1888, as a symbol of the mineral wealth of this state. But in 1921, as football became more popular, there were complaints from the students that silver and gold did not look good on football jerseys. In fact, silver and gold ended up looking like dirty gray and dark yellow. It wasn't until 1959 that the football team changed its jerseys to black with yellow. And although the football team seems to have set the trend with its color choice, CU still has the official colors of silver and gold.
Idaho has the same thing, silver and gold but they wear black and gold.
Take a look at the colors of all the schools that use gold that doesn't pair it with a contrasting color:
https://www.1122productions.com/tradition/colors/