These attraction-induced structural changes are reflected in the volume fraction dependence of the far-field optical response (Figure ). The extinction lineshapes for attractive hard sphere at U 0 = 3k B T and intermediate volume fractions (0.10 ≤ η ≤ 0.30) are significantly changed from those of hard spheres, becoming more asymmetric and in cases bimodal. For η < 0.20, increasing U 0 causes ω res to blueshift, while attractions cause the peak frequency to redshift for η > 0.20 (see Figure ). This result is consistent with known structural trends of attractive hard spheres, which favor dimers (blueshifted) at low packing fraction, but rapidly transition to larger, higher-coordinated clusters (redshifted) at higher volume fraction. Adding attractions broadens the spectral linewidth W at all η (Figure ). The stronger the attractions, the more sensitive the lineshape, ω res , and W become to changes in volume fraction, with the most prominent changes occurring at intermediate η. Meanfield theory incorrectly predicts no dependence of optical properties on U 0 , since it does not consider particle structural correlations. Qualitatively, including quadrupoles has the same effect on the extinction spectra as increasing interparticle attractions. Compared to p-truncation, the Q-truncation spectral lineshapes become more asymmetric and even bimodal at intermediate η (Figure ). Similarly, inclusion of quadrupolar contributions causes ω res to blueshift at low η and redshift at high η (Figure ), while it results in spectral linewidth broadening at all η, with changes strongest at intermediate η (Figure ).