Whilst I like Bart's answer for this instance, I would make a suggestion for a slightly different circumstance.
When searching for products, style/colour should come first
In the example you've given it looks like we're just about to go to checkout, we've found what we want and would like to take the next step. Prioritising Bart's way works well here as the customer has already decided on the item they wish to buy.
Prior to this I would imagine you would have some sort of search or filter feature for users to find the clothes that they're looking for. 'Display all clothes with xy properties'. In this event I would make the case that it's better to mirror internet shopping's offline counterpart - 'I want a red t-shirt, let's see if they have one/oh, isn't this a nice red t-shirt. Is there one in my size?.'
Typically (not always, I'm just thinking majority), people do not go shopping for size medium t-shirts, but they do go shopping for red t-shirts. Defining properties tend to come first with utility later. 'I need some black brogues... in size 10'
So, by this logic you should prioritise style/colour over size prior to getting to the individual product pages.