The players are beautiful but not sure about their outfits.
Well, it is obvious that, as far as my remark goes, the model is of importance too

, but, in general, it depends how you look at a tennis outfit.
For me personally, there are several lines of thought, when I judge whether an outfit is beautiful, but most of the time it is a complex of circumstances and details, that need to be presented to consider it as such.
Let us take the very first outfit (of Federer at Wimbledon) that I posted in this thread.
What makes it a true standout is the combination of the following:
White is the "uniform" of the tournament = tradition associated with purity, gentleman behavior
Green accents (the Nike logo) are representing the surface specific colour
The fact, that it is Federer (a legend of the sport, genuinely upholding the traditions of the sport in both playing style and manners and a master of Wimbledon) adds to the symbolic behind the outfit.
Also white and grass = instant classic.
In most (if not all) other settings in the modern game the "all white" outfit would have been inappropriate and not nearly as striking.
And, if we take a moment to compare two players with somewhat different styles in Federer and Nadal I would venture to say, that on Federer the white outfit sits better due to his finesse and touch (with which the Wimbledon tournament has always been associated), compared to Nadal's brute style. This is not a dig at Nadal, whose outfits that expose more arm and feature more striking colours are much more suitable for him than for Federer (I cannot even picture Federer sporting an "armless" look with success).
If we take Dimitrov's black and white outfit, there are a couple of things, that work in its favor:
First, the idea for a monochromatic look is very good in times, when virtually everybody is wearing striking colours. It conveys soberness and in a way it says, well, I am here to do business and I have a long way to go. IMO this fits perfectly the image of Dimitrov as up and coming player, who hasn't achieved much yet.
The use of patterns in this outfit is also quite striking. The angled (bigger) patterns starting from the extremities of the player (shoes, wristband) that morph into smaller patterns (the core) and at the end into an all white at the top of the outfit.
The use of the patterns to underline the logo - white swoosh on massive black background and black swoosh on white background literally underlined and visually supported by the pattern under it.
The special circumstances being represented by the blacked racquet, which compliments perfectly the rest of the outfit.
In the pictures of Hantuchova in most of them she sports black shorts which accentuate even more her slim built.
Black also helps with the vivifying of whatever colours might be presented, and that helps, especially with players, who are wearing lighter colours (like the sky blue in her outfits) and have white complexion.
I personally find the black accents (in the fourth picture) quite good as they offer 1) a link between the upper part of the outfit (top and head wear) and the bottom part of the outfit without being too prevalent 2) again, underline her slim look.
The third picture I could only describe as a whole outfit, because it so much fits the idea of summer - dark complexion of the skin of the player is perfectly matched with warm/hot colours of the tank top and head wear. The tank top is not of solid colour, so there is something going on there as well without being obtrusive (I think it is some kind of floral motive too, so that helps with the "summer" idea).
Again, the dark shorts are accentuating the slim look (nice play with the pattern there as well) and there is also a nice link between the shoes and the head wear with the red accents. It also helps that the player is wearing in a relatively discreet manner the national colours of her country on her shoes.
All in all, it is widely a matter of preference, but some outfits stand out as more "logical" or fitting in certain environments/contexts.
The waistcoat was a tad OTT, no?
That waistcoat is a f*****g abomination.