I'm no expert in these matters either, but Lynch and Livingston are, and they say that clouds absorb practically no light at all.

Before we can account for why the Sun appears yellow to us, two "facts" have to be accepted:

1: When the Sun is high in the sky, it is white.
2: When the Sun is high in the sky, humans perceive it as yellow.

From these premises, two things follow:

1: The Sun's yellow appearance must have something to do with human perception or psychology (since the Sun isn't actually yellow)

2: The Sun's yellow appearance must also have something to do with the extreme brightness of the Sun (otherwise clouds, pieces of white paper, and other things which reflect all wavelengths of sunlight equally would look yellow).

So far, the best explanation I have come across that takes both of these into account is robin's observation at the top of this thread: namely, when you look at a bright white light for a few seconds, it leaves a yellow after-image on your retina. I've tried this for myself and it's true. Look at the Sun, and for several seconds afterwards you will have a bright yellow blob in front of your eyes.

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