What are jobs limited to from color-blindness in the army?

My boyfriend is in the process of enlisting and remembered hes had problems with color-blind tests in the past. He can see some but not all of the color-blind tests online.

We also read that you can be color deficient and still get good jobs…

But for worst case scenario, if he is completely colorblind which jobs would he be able to get and what are his chances of being able to be a cavalry scout?

Any tips, experiences or statistics are welcome.