Greg Laden recently posted on Green stone beads at the dawn of agriculture, an archaeological study of coloured beads, how the colours change over time, and what all that might actually mean for people interested in the evolution of people (which may well be all of us). There’s a nice chain of reasoning there, from the frequency of different colours to the times at which those frequencies change, to connections with fertility. Money quote, from the paper, via Greg:
We propose that the green color mimics the green of young leaf blades, which signify germination and embody the wish for successful crops and for success in fertility.
But go and read the thing in full.