Note on the left that the color is deep pink in the interior of each lobe but fades to pale pink at the edges. what does this change in color represent?

The change in color represent the Electron-density distribution of a 2p orbital. Electron density is the measure of the probability of an electron being present at a specific location. The electron density of a 1s orbital, on the other hand, is a maximum at the nucleus. The same diagram for the 2p density distribution is obtained for any plane which contains this axis.