Paint by number or painting by numbers are kits having a board on which light markings to indicate areas to paint, and each area has a number and a corresponding numbered paint to use. The kits come with little compartmentalised boxes where the numbered colour pigments are stored. The users are encouraged to wash the paintbrush every time a new numbered colour is being used. The kits were invented, developed and marketed in 1950 by Max S. Klein, an engineer and owner of the Palmer Paint Company of Detroit, Michigan, and Dan Robbins, a commercial artist.