Abstract: The system consists of a board with sockets and an assortment of tetrahedral pegs having a regular obverse face and a reverse side in the form of a triangular shank that inserts to a matching fit in one of the sockets. When the pegs are inserted into the board or first element the adjacent faces of the pegs make contact so that no gaps exist between adjoining edges. Each of the faces, or a part of each face, if divided into more than one field, is uniformly tinted in one of a set of repeatable colors or polychrome or monochrome shadings.