Plants appear green due to the presence of the pigment chlorophyll.
Step-by-step explanation:
Plant cells have some differences from animal cell. Presence of cell wall and the cell organelle chloroplast, both of which are absent in animal cells is one such difference. The cell organelle chloroplast contains the pigments like chlorophyll A,B,C,D etc.
Chlorophyll pigment is responsible for trapping the energy of the sunlight. Chlorophyll A absorbs constituent color radiations of the sunlight except green color. Thus green color radiation is what it reflects and thus it appears green in color.
It is the presence of chlorophyll A in plenty that gives the characteristic green color to plants.