Answer
The ejection of an electron depends on the interaction of one photon with an electron. Photons of red light are less energetic than blue photons.
Work Step by Step
For photons, E = hf, where E is the energy, h is Planck's constant, and f is the photon's vibrational frequency. Red light has a lower frequency than blue light.
Because only one photon is needed to eject an electron and give it energy, an intense but low-frequency red light has no success in ejecting electrons, because each photon has to act alone.
This is discussed on pages 585-587.
