After Newton amused himself that light was nothing but whizzing corpuscles, he immediately realized that he had just opened a fresh can of worms. Why then don't we see light as just that, speeding corpuscles? Why do we see a 'static' bright colors? This seems to be the question that bothered him when he said that 'we don't have a clue as to how the brain creates the phantasm of colors'. Like many people, especially after him, he erroneously concluded that 'color is a phantasm created by the brain'. He cared less to find evidence for that. Maybe if he found it, he would check how the brain does this wonder!
First note that we can't realy separate 'color' from 'light'. A 'colorless light' will not appear as light at all! So when someone delegates colors to the brain, he has actually delegated the whole thing to the brain. In effect, he denies what we thought he was going to explain! Light, he says, is a 'who knows how the brain creats illusions from impingings and/or vibrations'. But then as 'evidence' that his theory is correct, he points to the very same thing he is also trying to deny! Light must be particles, Newton insisted, because we see that the very light is collimated. In other words according to what Newton gives as evidence for his corpuscles theory of light, if light is ever whizzing corpuscles, then the corpuscles themselves are made of light! We need light to understand light!
The erroneous philosophy Newton unwittingly spearheaded comes because many people (Newton included ) tends to confuse 'existence' with 'spatio temporal presence'. Below I will elucidate on 'spatio temporal presence'. A corpuscle is 'spatially present' in that it is 'somewhere in space'. A moving corpuscles is ' temporaly present' in that it exist in a given location in a fraction of a second. So how a corpuscle can be said to exist is supposed to be easy to realize. So saying that 'light is moving corpuscles' is supposed to help us understand how such a thing can exist 'out there' simply because existence 'out there' is, according to them, the same thing as 'spatio-temporal presence'. But this philosophy is erroneous!
On one hand, Newton did correctly note that there is an analogy between light and speeding corpuscles. But he erred in thinking that this analogy will help him unlock the secret of light. He was supposed to also consider a case where the analogy would help him unlock the secret of movement of corpuscles. In other words he should not have presumed that we can understand movement by just looking at a moving object, if we cannot understand light by just looking at a blazing torch. I know this approach requires some boldness! Then he would be lead to the better idea that the mind reconstruct both movement and light from a deeper, more fundamental reality. This way, it becomes a bit easier to figure out how 'the brain generates the phantasm of colors from the impingings and/or vibrations due speeding corpuscles'. It does so in 'who knows how it might also creat an illusion of motion from colors'.
Notice also that we realy cannot form an idea of object without light! In 'spatio-temporal' sense, we might be tempted to define 'object' as 'that which has a shape'. But 'shape' in turn is defined by the finitness of the region out from which light is emitted or reflected. The concept of an object without light will be absolutely colourless and thus indistinguishable from the empty background! So to understand an object, we must first understand light! So the idea that 'light is speeding corpuscles' is circular! literally, it means 'light is speeding specks of light'!!
The same reasoning (mutasis mutandis) can also be applied to the idea that light is a wave. The evidence that a physicist offers is the famous 'double slit experiment'. He points to alternative patterns of 'brightness' and 'darkness' and then tells you that this shows that light is a wave! The blue light has different spacings from the red light etc. But when you close examine, you find that you are already seeing a 'blue' thing etc! If light is a wave, then the evidence indicates that it is a 'wave of light' itself! The light waves by rapidly changing its brightness throughout the space! So wave is more of what light does than what it is! Again the reasoning is circular! Saying that color blue is 'a wave of a certain frequency' is actually saying that color blue is the 'rapid alteration of the color blue'! We need the color to understand the color!