Montessori colour tablets are used to teach children the names of colours and refine their visual sense. Box 1 teaches the primary colours, Box 2 teaches primary, secondary colours, pink, brown, black, white and grey. Box 3 has shades of the above 9 colours except for black and white. The child has to arrange the shades in order.
We made a Box 1 set some time ago. We bought a wooden strip of wood the same width we wanted the tablets to be, cut them to length and sanded them well. Then we put sellotape onto the sides and painted over both sides with acrylic primary paints. We had to apply several coats to make sure the colour was absolutely opaque and even. We painted two red, two yellow and two blue to make the Montessori Colour Box 1. I made a little origami paper box to contain them but it turned out to be too weak and it broke as soon as a child used the tablets.