Cephalopod color change is important for concealment and communication and is primarily controlled by chromatophores, pigment-containing sacs that expand and contract. The metabolic cost of the chromatophore system, and thus color change, in octopuses is unknown, but would reveal principles of how camouflage works, affects cephalopod energy budgets, and relates to their evolutionary history. In this study, we investigated the metabolic cost of chromatophore expansion in Octopus rubescens by performing respirometry on excised sections of chromatophore-containing skin and using light-activated chromatophore expansion (LACE) to periodically expand the chromatophores in the skin. We placed excised skin in a 612 μl respirometer and measured oxygen consumption while we stimulated chromatophore expansion by lighting the skin with intense blue light for 5 minute periods followed by 5 minute periods without blue light during which chromatophores contracted. The respirometer was under a dissecting scope, so micrographs could be taken of the skin. We used the micrographs to count the number of chromatophores expanded between periods when the blue light was on and off and used those counts to determine oxygen consumption per expanded chromatophore. We used whole preserved octopuses to estimate the total number of chromatophores on a whole octopus, and thus relate chromatophore oxygen consumption to total metabolic rate.