A white material reflects all colors. A color filter absorbs certain colors of light and allows others to pass through. Red, blue, and green are the primary colors of light. Mixing these colors can produce all of the colors of the spectrum. Our eyes have cells in the retina that react to colors of light.
Some cells react only to red.
Others react to green. Still others react only to blue. If the retina is struck with equal amounts of red, blue, and green light, we see white. Yet if the retina is struck with only red and green light, we see yellow. Colors that result when you blend paints are different from the colors that result when you blend colored lights.