thanks kenny. I've been experimenting with this too, and the amount of potential work here is huge: I have to specify a variation - and add image apparently - for each colour/size combination. Currently (on my homegrown cart), have a drop down to pick a male or female size per colour. Using that system I have 11 products (read:colours) in the category. Using variations I'd have to enter details for over 100 products.
Even if I add each colour as a separate product in woocommerce, I'd still need to double the number of product entries - because the sizing for male and female is different. I cant have a male/female variation because the 2nd dropdown box needs to change depending on the selection of the first.
And in fact thats another way of framing what I need: to dynamically change the second dropdown box depending on an initial selection.