I don't think the colour matters enormously. I should think there were lots of variations, so I'd say, just use whatever looks good!
It's interesting that you showed the picture of the round houses. You're right that these would not be right for Anglo-Saxons; they are more Romano-British or even pre-Roman. However, if you were interested in making a city set using these houses as well, I could definitely use those too (for the Romano-British).