Experiments with tobacco and grapevine leaves having different color due to varying stages of senescence showed that leaf hue is significantly linearly correlated with chlorophyll content up to 80% loss of pigment. Samples from leaves with more pronounced loss of chlorophyll did not fit into this linear relationship, and the hue data set as a whole followed a saturating exponential dependence on chlorophyll content. In leaves with less than 80% chlorophyll loss, the hue parameter was also proportional to the photochemical yield of photosystem (PS) II measured in the light. These results suggest that leaf hue measurements offer a fast, high-throughput initial screening system to precede more specific but more time consuming photosynthesis measurements, with the possibility of applications not only for senescing plants, but also for stress conditions accompanied by chlorophyll loss.