Spray coating processes require accurate control over the impact of highly complex and viscous liquid droplets on solid surfaces. Here we use theory and experiments to investigate aqueous colloidal dispersions and acetone-based solution droplets impacting solid surfaces of varying wettability. Over a range of impact speeds and effective viscosities, We ∼ [special characters omitted](1–300) and Oh ∼ [special characters omitted](0.01–1), we observe that the spreading dynamics follows a decaying function in characteristic times, D/U, where D and U are the initial drop diameter and impact speed, respectively. The spreading diameter decays to an asymptotic value referred to as the maximum spreading diameter. The maximum spreading diameter β_max during inertial times [special characters omitted](D/U) is shown to be in good agreement with three models available in the literature. The centerline height dynamics reveal an unstudied resonant regime for We ∼ 30. In this regime, the centerline height sinks below the formation of a thick rim. As the centerline height recovers, the rim height h_r is shown to increase linearly with time for our complex liquids and equivalently viscous Newtonian solutions. Immediately following this inertial driven regime, the drop continues to spread by capillarity until equilibrium. The transient spreading dynamics of an aqueous colloidal dispersion on nearly fully wettable substrates reveals that Tanner's law, d( t) ∼ t^1/10, is approached but not in a consistent manner. The effects of residual inertia influence these short term spreading dynamics of both colloidal dispersions focused on herein and glycerol/water solutions. In particular, the spreading dynamics is found to obey a robust power law d(t) ∼ C(t/μD/σ)ⁿ, where C is found to be an [special characters omitted](1) constant and 1/9 [special characters omitted] 1/5.