Abstract: A system and methods by which the state or condition of an object may be determined through the analysis of spectral bands. One embodiment of the present invention automatically detects a first spectral band having an absorption that is highly sensitive to the color of the object, such as that produced through a colorant or a pigment of interest. The embodiment then may automatically detect a second spectral band having absorption sensitive to color resulting from other colorants or pigments other than the pigment of interest. A third spectral band may also be automatically detected that is sensitive to reflective differences caused by variation in conditions. Subtracting the absorption in the first band by the second band and multiplying the result by the amount of light reflected in the third band results in the index. The index can be highly correlated with the concentration of the colorant of interest.