I. Schur and G. Schur proved that, for all completely multiplicative functions f : N → {−1, 1}, with the exception of two character-like functions, there is always a solution of f (n) = f (n + 1) = f (n + 2) = 1. Hildebrand proved that for the Liouville λ-function each of the eight possible sign combinations (λ(n), λ(n + 1), λ(n + 2)) occurs infinitely often. We prove for completely multiplicative functions f : N → {−1, 1}, satisfying certain necessary conditions, that any sign pattern ( 1, 2, 3, 4), i ∈ {−1, 1}, occurs for infinitely many 4-term arithmetic progressions (f (n), f(n + d), f(n + 2d), f(n + 3d)).The proof introduces graph theory and new combinatorial methods to the subject.