Colour Institute

Computer graphics is an excellent tool to create demonstrations, but exactly because of the
ease of creating nearly any effect it may not be very convincing when we try to illustrate
the  separation,  mixing  or  interaction  of  colours. While  the material at  the  courses  of  the
SENAI/CETIQT  Colour  Institute  is  presented  in  numerous  Power  Point  slides,  in  our
classroom demonstrations we illustrate the various concepts by showing real examples. In
this paper we  shall  describe  the demonstrations  used  in our  colour  courses  for engineers
and  designers; showing  the  spectrum  and  illustrating  selective  absorption,  diffuse  and
specular  reflection,  subtractive,  additive  and  partitive  colour  mixing,  the  interaction  of
colours  and  the  phenomenon  of  coloured  shadows. The  demonstrations  generally  don’t
need any special device beyond a conventional slide or overhead projector and some well
selected dichroic or other colour filters. For partitive mixing a rotating disc is used.