Who am I?

Leaves are green because of me.

Chlorophyll

Plant cells contain a specific organelle called "Plastids". These plastids contain some pigments that impart specific colours to plants. One such plastid is "Chloroplast", it contains a pigment called "Chlorophyll" which imparts the green color to leaves.

There could be the presence of other pigments also that impart different colors like, carotene gives orange color to carrots, Betalains imparts dark pink colour to Beets etc.