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The first color image from the surface of #Mars, captured by NASA's Viking 1 lander #OTD on July 21, 1976. On the left here is the initially-released version, which was calibrated too far red. The one on the right is a more natural-color view of the same scene.
This is based on several investigations of the calibration of this image, as well as others captured by various surface missions over the years, but mostly this analysis by @DDAVISSPACEART http://www.donaldedavis.com/PARTS/MARSCLRS.html
Science journalist @coreyspowell wrote on this a few years back for Discovery too. True color on Mars has been a moving target for a long time, and may never truly be nailed down until humans see it with their own eyes. https://www.discovermagazine.com/the-sciences/what-color-is-the-red-planet-really
I say that, but even then our color perception varies from person to person, not to mention across various imaging devices and the screens the images are shown on. (Go shopping for TVs or monitors at a store and you know what that looks like.)
Also Mars, like Earth, has varied landscapes and is not the same color everywhere. Also it can change depending on the time of day (sol). Some places are redder or more orange or yellow. It depends. Mars isn’t one thing.
