Consider how we experience what we call "reality":
We don't actually see. Light enters the eye and stimulates specialized light receptors (rods for black&white, cones for color). When stimulated, that receptor sends a nerve impulse to a specialized area of the brain that interprets those impulses as seeing.
We don't actually hear. Oscillating air cause the eardrum to vibrate. Those vibrations are passed via three small bones (hammer, anvil, stirrup) to the cochlea and sets up vibrations in the cochlear fluid. The fluid, in turn, causes specialized "hairs" to vibrate and those hairs send a nerve impulse to a specialized part of the brain which interprets the nerve impulses as sound.
All senses (and there are many more than five) work this way. The big point is that the nerve impulses from those receptors are IDENTICAL in nature. It is the part of the brain that receives the impulse that interprets it. If you could switch the nerves from the ear to the optical part of the brain, you would "see" sound.
What is color? It isn't real. Yes, different wavelengths of light are detected by the cones but our perception of red, green, blue, etc. results from a section of the brain that receives an impulse from a particular receptor. Again, the impulses are IDENTICAL. In fact, we only see three "colors", namely red, green and blue because those are the three types of cones that we have. Other colors result from the stimulation of more than one type of cone and, again, are interpretations of the brain.
How much of the external world do we actually know? In truth, none of it because our sensations are all filtered by our brains. It is impossible to imagine a color that you have never seen. Many birds and insects have receptors that respond to ultraviolet. What does it look like? If their perceptions are at all like ours, it looks like a color that we have never seen. We can use film that is sensitive to ultraviolet but we don't actually see it. Instead, the film converts UV to a color that we can see.
Astronomers deal with this all the time. They realized, long ago, that most of the light in the universe falls outside our limited perceptions of wavelengths. So, they scan the skies for radio waves, UV, X-rays, and gamma rays. We can devise methods of converting those things to visual media that are visible to us, but we don't really experience them.
Patients undergoing brain surgery are generally conscious (the brain has no pain receptors so only local anesthetics are needed). When a visual area of the brain is stimulated with a mild electric current, the patient sees things. To the patient, this is just as real as "actual" sight.
In conclusion, our senses give us the illusion that we can know our surroundings. This is only an illusion.
