I have no doubt that the theories had been vaguely floating about before as obvious suggestions of common sense; for nothing in thought is ever completely new.

But at that epoch they were systematised and made exact, and their complete consequences were ruthlessly deduced.

It is the establishment of this procedure of taking the consequences seriously which marks the real discovery of a theory.

Systematic doctrines of light and sound as being something proceeding from the emitting bodies were definitely established, and in particular the connexion of light with colour was laid bare by Newton.
The result completely destroyed the simplicity of the 'substance and attribute' theory of perception.

What we see depends on the light entering the eye.