Real-world lighting often consists of multiple illuminants with different colors. Separating and manipulating these illuminants in post-process is a challenging problem that requires either significant manual input or calibrated scene geometry and lighting. In this work, we leverage a flash/no-flash image pair to analyze and edit scene illuminants based on their color differences. We derive a novel physics-based relationship between color variations in the observed flash/no-flash intensities and the chromaticies and surface shading corresponding to individual scene illuminants. Our technique uses this constraint to automatically separate an image into constituent images lit by each illuminant. Each light component can then be edited independently to enable applications like white-balance, lighting editing, and intrinsic image decompositions. We demonstrate that this technique outperforms state-of-the-art techniques for some applications and enables other applications that are not possible with previous work.