Copyright law and patent law (whether or not you agree with their efficacy, overall) are at least explicitly designed to protect creators and their business interests. However, trademark law differs in that its primary purpose is consumer protection: trademark exists to allow for product marking so that consumers can be confident about the origins of products and all their attendant considerations, ranging from quality of product to the reputability of the company supplying said product. For instance, you want to know that the batteries in your remote control won't explode, and if you see the label "duracell" or "energizer" on the battery, you can be reasonably sure that there is a responsible company behind their manufacture.
However, the consumer is actively harmed by the court's grant of the exclusive right to make shoes with red soles to Louboutin. Not only is it unlikely that the sort of consumers who are going to spend that type of money on shoes are likely to unintentionally buy knockoffs -- we can all reasonably expect that Nordstroms is not stocking its shelves with counterfeit goods -- but when these consumers do buy knockoffs, they know quite well they are doing, and it is an intentional act. However, that is beside the central point, which is the fact that now, if someone who cannot afford to buy a red-soled pump from Louboutin wants to buy a red-soled pump from a competing manufacturer, the competing manufacturer would be committing trademark infringement by supplying said shoe. Which is ridiculous in my eyes. So, as a result, this trademark decision simply favors those with disposable income over those who may be fashion conscious but not made of money, and I simply cannot see any conceivable counterbalancing consumer protection concern.
Here's a simple test when buying luxury brands:
1. While you are holding the item you are purchasing, look around you.
2. Are you standing in a store, the name of which you recognize? Then it is real.
3. Are you standing behind a van or in front of a folding table on the street? Then it is fake.
Trademark protection over color choices in functional design elements is simply unnecessary for brand protection or consumer protection in the world of high fashion. There are plenty other ways to identify fashion brands, such as logos and tags, that accomplish brand identification perfectly well, without having the negative externality of limiting fashion choices for all but the very wealthy. Let me be very clear: I do not believe that competitors should have the right to claim that their own knockoffs are Louboutins - but I don't see a reason why Steve Madden shouldn't be able to make red-soled pumps under his own label as well. Personally, I'd also argue that this is a functional design element, and therefore ineligible for trademark protection as a matter of law - but that is another matter for another post.