The present concept is a portable colour sensor for measuring colour of a substrate that includes a single flat printed circuit board with a top and bottom side which includes at least one LED light and one colour sensor and at least one light pipe receiving light from the LED and transmitting it onto a substrate at an angle theta. It also includes a tube frame including an optical tube for receiving light reflections from the substrate and directing the reflections to the colour sensor. The light pipes and the tube frame, are mounted and compression fit between the printed circuit board and a lower housing.