sentences:  The acceleration voltage is used to determine the energy of the electrons; lower-energy ones are absorbed in the top layer of the phosphor, while some of the higher-energy ones shoot through and are absorbed in the lower layer.So either the first color or a mixture of the first and second color is shown.With a display with red outer layer and green inner layer, the manipulation of accelerating voltage can produce a continuum of colors from red through orange and yellow to green.