A false color image is an image that uses visible colors to represent portions of the electromagnetic spectrum outside the typical range of vision. This allows the image to provide data that is otherwise invisible to the naked eye. Astronomers use this technique to display infrared radiation in deep space imagery.
In a true color image, the colors red, green and blue represent their equivalents in the visual spectrum. This produces an image that looks approximately the same as it would to a physical observer, although variations in imaging and display make it difficult for a true color image to be perfectly accurate.
False color images use one or more of the display colors to represent an invisible spectrum of energy. For example, in infrared photography, red may represent the highest intensity of infrared radiation, with blue representing the least intensity. This converts a greyscale infrared image into a vividly colored representation of the electromagnetic spectrum, providing more detail for the observer.
False color can be used to represent multiple channels of data. For example, the color red may be used to represent infrared, while the color green represents red visible light, and the color blue represents green visible light. This technique is used to highlight areas of dense plant growth in aerial or satellite photographs, allowing the viewer to quickly gauge the health of forests and ground cover.