Match each crayon plaque with the corresponding illustration showing the same colours. The control of error is present.
Modified from Toys for Life (made by Nienhuis).

Visual observation of colours and quantities

Prepared crayon plaque and illustration on computer, printed out & laminated.
Prepared self-checking line patterns on computer, printed out & laminated, then sticked to back of illustration plaque.
Storage box were folded out (origami).