Dynamic and static properties of strongly asymmetric binary mixtures of spherical colloidal par-ticles are studied using Brownian dynamics (BD) computer simulations and analytical methods. Our study comprises mixtures of super-paramagnetic particles confined to an air-water interface, and mixtures of colloidal hard spheres. The strong interaction asymmetry in the magnetic parti-cles leads to unusual features in the pair distribution functions, and to hydrodynamically enhanced self-diffusion. Rotational and translational diffusion of a tracer component in a hard-sphere host dis-persion is examined in dependence on the tracer-host size ratio and host concentration. A continuum limiting behavior is reached for progressively enlarged tracer size, characterized by Stokes-Einstein (SE) relations between tracer diffusion coefficients and viscosities. To reach the continuum behavior, larger tracer sizes are required for rotational than for translational diffusion.