We study how moderate rotation affects photometric observables in beta Cephei stars. The most important effect is the rotational mode coupling of modes with harmonic degree, l, differing by 2 and the same azimuthal order, m, if the frequencies are close. This is not an uncommon situation among unstable modes in beta Cep stars. Positions of the coupled modes in the amplitude ratio vs. phase difference diagrams are aspect, i, - and m-dependent. Inference from the diagrams becomes more complicated.