Colour is represented as Spectral Power Distribution (SPD) in physical 3D world scene. A set of three discrete values, triplet, such as RGB represents colour in digital 2D image. RGB values are derived from SPD using colour transforms. The physical basis of digital colour is SPD. Colour processing in natural 3D world scene could be thought of manipulation of SPD. We explored different colour enhancement techniques based on derived SPD. Examples showing the spectral based enhancement operations negative, flipping of wavelengths, morphological operations, changing illuminants, increasing the brightness, smoothing, edge detection etc. with experimental results on real images. The results appear to demonstrate that our proposed approach successfully simulates physical processes. Further, the approach outlined in this paper leads to numerous significant applications in computational photography.