Foliar colour is the resultant of physical interaction of light on structureswithin and on surface of leaves. Quantitative representation of foliar colour provides a means to express the condition of crop.The Red, Green Blue (RGB) values from raw digital photographs of rice crops were transformed to CIE L a b colour space in Matlab®. Authors present results that convey strong relation between colour dimension 'a' of Commission Internationale de l'Eclairage (CIE) L a b colour model and Green Red Vegetation Index (GRVI). More than 90% variability of Green Red Vegetation Index (GRVI) of rice crop was explained by 'a'. This provides an affordable means for ground based remote observation to monitor crop condition in real-time.