ILL 1969 Problem 58

$(SWE 1)$ Six points $P_1, . . . , P_6$ are given in $3-$ d imensional space such that no four of them lie in the same plane. Each of the line segments $P_jP_k$ is colored black or white. Prove that there exists one triangle $P_jP_kP_l$ whose edges are of the same color.