21 March is the International Colour Day.
Visual perception is the ability to interpret the surrounding environment by processing information that is contained in visible light. Colour is greatly influential in people’s lives and also one of the channels that contributes to the perception of reality.The day chosen for the adoption of an international day of colour and light was March 21st because this day is the also the "equinox" – aequus (equal) and nox (night). Around the equinox, the night and day are approximately equally long, symbolically relating to the nature of light and darkness, light and shadow expressed in many human cultures.
Website of the International Colour Association: