Ta-da! here's the first almost-complete Up-Down Entrelac sock (I'm still thinking of ways to finish the top of the cuff). This sock weighs 40 grams. I have 124 grams of yarn left, which means that there should be enough for 3 more socks, or another complete pair if the colors are mixed up!
I've therefore decided to use the colors randomly for the mate for a pair of wildly mis-matched socks.