A leaf appears green because it contain an abundance of chlorophyll which is a green pigment.
A green summer leaf contain so much chlorophyll that other coloured pigments in the leaf are
masked out. Sunlight controls the amount of chlorophyll produced, so as autumn days grow
shorter less chlorophyll is produced. This gradual reduction of chlorophyll allows other
pigments in leaf to be revealed. During the autumn levels of chlorophyll decreases, as well
as increased sugar concentration which cause an increase production of anthocyanin.
Anthocyanin a redish pigment which gives leaves their red autumnal colour.
The spectrum graphs below show transmission plots, which is the measurement of light of
varying wavelength that is able to pass through the sample. This is typically the inverse
of absorption plots, which is the measurement of light that is absorbed by the sample.
Also shown below are CIE colour space chromaticity diagrams which plot the actual perceived
colour of the sample.
In plants there are two types of Chlorophyll, namely Chlorophyll-A and Chlorophyll-B.
Primarily it is Chlorophyll-A that is responsible for performing photosynthesis, the role
of converting light energy to chemical energy such as the production of sugars.