Chlorophyll a is the primary plant pigment capturing light
forphotosynthesis and is a green color. how is this so when most
lightenergy for photosynthesis derives from red and
bluewavelengths?

Chlorophyll a absorbs maximum light in blue and red regions of the spectrum while reflecting the green light.

Explanation:

The light reflected by any object reaches our eyes. “Chlorophyll-a” molecules are the pigments that do not absorb the green light and reflect it. The reflected green light imparts the chlorophyll-rich leaves a green color.

Since the absorption peak for Chlorophyll-a lies in red and blue regions of the spectrum, the maximum rate of photosynthesis is experienced in the presence of red and blue wavelengths.

The light absorbed by Chlorophyll-a drives light reactions to produce ATP and NADPH which in turn are consumed during the Calvin cycle to fix CO2 into glucose.