Re: why are some leaves greener then others?

Leaves contains other pigments in addition to green chlorophyll that can affect 
the overall shade of green. Carotenoids are red or orange pigments. 
Anthocyanins vary widely in color depending on the cell pH (acidity) and can be 
yellow, red, purple or blue. A common exercise uses the anthocyanin in red 
cabbage as a pH indicator. Some leaves are not even green because the 
chlorophyll is masked by the other pigments, for example purpleleaf plum, blue 
Colorado spruce, and coleus.

Other factors that could affect the shade of green are leaf hairs, leaf 
thickness, and the leaf chlorophyll concentration. There is also more than one 
type of chlorophyll which differ slightly in color. 

Reference


Red Cabbage


Carotenoids and Anthocyanins in Fall Leaf Colors