Soil color is one of the most useful soil properties for assessing and monitoring soil health. Here we present results of tests of a new soil color app for mobile phones. Various smartphone cameras (SPCs) were tested under sunny and cloudy conditions and compared with visual estimates using Munsell color charts (MCCs). The measured and estimated soil colors were then compared with the “true” colors determined using a spectrophotometer. The results indicated that soil color determinations based on SPC measurements under both sunny and cloudy conditions were as good as those obtained using the MCCs. The accuracy of the SPC measurements was affected by the natural illumination conditions, with higher accuracy in the sun than where clouds were present. Our results also indicated that the SPC measurements completed in the sun provide higher precision (lower variance) than SPC measurements completed under cloudy conditions or estimates based on MCCs. These results suggest that mobile-device cameras have great potential to allow non–soil scientists, and others lacking access to color charts, to determine soil color.