I found an article loosely related to that topic in : Weischet, W.: Einführung in die Allgemeine Klimatologie. G.B. Teubner, Stuttgart (1979) (german language, sorry, I don't have anything in english on this topic). There a diagram of sun's spectral energy distribution is given which shows that towards longer wavelenghts (from the "green" maximum) more energy is emitted than towards shorter ("bluer") wavelenghts. This can, together with the construction of our optical sensors, explain the yellow appearence. On the other hand, the EM absorption of water molecules is stronger at longer wavelenghts, so maybe the two effects just even themselves to produce the clouds' white appearance. I don't know about the absorbance/reflection properties of moon dust, Mr. Plait should have better grasp to hard data on that than me. Well, if the BA doesn't have a satisfying explanation, why should I come up with the ultimate answer?