The three primary colors of color light are red, green and blue; So red, green and blue? When three colors are irradiated on white paper (Figure A), white will appear in the middle overlapping area;

The circular spots on the ground under the shade of trees are images of the sun formed by sunlight passing through holes in dense leaves. It is a real image, formed by the straight-line propagation of light.

So the answer is: blue; Linear propagation; Real image.