Why are the outer leaves of the cabbage green and the inner ones white?

A cabbage head is a modified shoot, consisting of a stem (stalk) and a large number of modified, tightly adjacent leaves. The leaf is known to be the organ of photosynthesis (the formation of organic substances from inorganic ones). Photosynthesis requires light and chlorophyll. If there is not enough light, then chlorophyll is destroyed. Therefore, the top leaves of the cabbage, which receive enough light, have chlorophyll, green. The inner leaves are white, as there is not enough light for them.