Remove colour from an interface and every convention built on it breaks. No blue link, no red destructive action, no green success state.
What replaces it
Rule weight, scale, negative space, and inversion. A hover state that flips chalk-on-ink to ink-on-chalk is louder than any tint, which means you can afford it in fewer places.
The discipline it forces
You cannot decorate your way out of a weak hierarchy. If the page does not read without colour, the structure is wrong.