The use of smartphones and digital cameras as color measurement tools is reported. Initially, a careful mathematical analysis of the intrinsic limitations of using an 8-bit RGB color space was conducted, determining the ΔE in terms of sensitivity and conversion error to the CIELab space. Metal coatings were subsequently analyzed under extremely different lighting conditions, obtaining equally different colors. The use of a colorimetric reference card, captured alongside the samples, enabled the minimization of these differences. The possibility of obtaining quantitative results using portable and widely available devices, such as smartphones, even in outdoor environments with uncontrollable lighting conditions provides a valuable analytical tool across various fields, including industrial, decorative, medical, and food applications, especially in the characterization of coatings. Eight-bit RGB devices limit sensitivity in the worst case to ∆E = 1.5. ∆E > 20, as measured by spectrophotometer and smartphone, which was reduced to ∆E < 5 after the proposed processing.