By: Daniel Overbey Color plays an important role in our everyday lives. It can influence our mental or physical state, change our buying habits, communicate instruction, warn us of hazards, and help define identity. However, color also plays an important role with managing energy and light. Consider a simple, flat, matte painted wall that is exposed to the sun. Unlike electric lighting, which will often generate light that is missing certain colors within the visible electromagnetic spectrum, the sun casts full-spectrum daylight upon the painted surface. For every portion of the full-spectrum (e.g., red through violet), light will either bounce off of the painted wall or be absorbed as thermal energy (i.e., heat). This is where color comes into play. The color of the wall indicates what portion of the full-spectrum is being reflected. For instance, a red painted wall indicates that the red portion of the visible electromagnetic spectrum is being reflected (while the rest of the light is being absorbed as thermal energy). If the wall is painted bright white, then the vast majority of the visible spectrum is being reflected. If the wall is painted pitch black, then most of the visible light is being absorbed. A paint’s light reflectance value (LRV) indicates what percentage of the visible spectrum will be reflected (e.g., LRV 40 means that 40% of the visible spectrum will be reflected). However, the color of the paint is an indicator of which portion of the visible spectrum will be reflected. This can come into play with green building in many ways – white “cool” roofs, dark solar absorbing panels, and bright white light reflectors are just a few common examples. While the visible light spectrum represents only a small portion of the electromagnetic spectrum coming from the sun, a basic understanding of color’s influence on energy and light is an important fundamental design concept and can improve green building strategies in numerous ways.