Spectral encoding / decoding methods using unique eigenvectors and physically meaningful values were explored. Three new methods such as, TrW6 consisting of 6 unique trigonometric functions, Lab2 consisting of two CIELAB, LabRGB consisting of CIELAB and RGB, were derived and compared against the traditional eigenvectors method. It was found that TrW6 and LabRGB showed almost the same accuracy as the traditional eigenvectors method. By using LabRGB, color characteristics can be estimated by only looking at its encoding signals and we do not have to exchange eigenvectors beforehand for exchanging a different population of object colors. LabRGB can be applied not only to spectral imaging but also to traditional tri-chromatic imaging world, so its usage is unlimited.