The red and the blue parts!
There are different photosynthetic pigments out there, but most plants do use a type of chlorofyl.
Below is a graph that displays which wavelengths (and thus color) is absorbed (taken up) by the chlorofyl.
Sunshine contains all the wavelengths (colors) but the plant pigment can only use a certain range of color for processes. You could see a plant as a growing solar cell!
The chlorofyl will absorb light of the Red side and the Blue side of the spectrum. This leaves us with green. What happens to the green wavelengths? Green is not taken up (absorbed) by the chlorofyl, and therefore is reflected. We can actually see that because plants are mostly green!