Sheet lightning The light within the cafeteria changes according to the season, the outside temperature and the time of day. In the interior space two parameters affect the light. Firstly, the season determines the colour of the light: the warmer the outside temperature, the cooler the colour of light; the cooler the outside temperature, the warmer the colour of light. Secondly, the time of day determines the brightness of the light. In the exterior space surrounding the cafeteria the same parameters affect the light, but in the reverse way.