Although the large Kerr coefficient of aqueous graphene oxide (GO) dispersions is quite attractive for electro-optical applications with low power consumption, the maximum birefringence of GO dispersions is not sufficiently high for actual display applications. Here we report that adding a small amount of larger GO particles (about 4 mu m) into a high-concentration dispersion of small GO (about 0.2 mu m) can improve the electro-optical sensitivity to an electric field and also the maximum birefringence. Large GOs induce the ordering of small particles and enhance the electro-optical switching. Large GOs have higher polarizability and are easily driven under an applied electric field, and the rotational motion of large GO particles leads to switching of surrounding small GO particles, improving the electro-optical performance. The binary mixture can overcome the limitations of pure dispersions of large GO or small GO particles; the former has high interparticle interaction, and the latter has low sensitivity to an electric field.