The wave lengths are processed so as to create and produce colour which is superimposed to its final interpretation. The interferometrical light wave interaction produces the real hologram.
The use of interferometry in holography creates an absorbing natural softness; colours harmonise in a manner that echoes the light waves of nature itself. This can only be visualised by viewing the hologram itself. A photograph cannot convey the richly immersive experience of regarding the hologram directly.