Wawrinka has been playing in a "highlighter" outfit: bright yellow shirt, bright yellow shoes, black shorts. I was wondering if any players have already complained about it. I would imagine this color combination should give Wawa some advantage by distracting his opps: the tennis ball being almost the same color as shirt/shoes. Moreover, black and yellow combo is known to command human attention on a subconscious level.
This is not the angle his opps are looking from. I think it's a ploy, probably more to annoy his opps but still a smart move by Wawa.
I used to think that WTA players screamed just b/c they liked to scream, but they actually try to "hide" the spin of their shot: a lot of the info is lost if you cannot hear the sound of the ball hitting the strings. Of course some of them just like to scream.