In the first figure, the surface absorbs all colors except for green light, which is reflected: so, the surface will appear as green to our eyes, because green is the only color which is reflected by that surface.
Similarly, in the second figure, the surface absorbs all colors except for blue, and so the surface will appear blue to our eyes.
In the third figure, the surface absorbs all colors, so it will appear black to our eyes (because no colors are reflected, and black=absence of colors).
In the fourth figure, all colors are reflected: this means the surface will appear white to our eyes (white= sum of all colors).
