They just add 'feel' to the brakes, before I got them fitted I found the brake a bit vague and spongy really.... 
It won't matter what colour you get really, because unless you intend to clean them every week, they all end up looking the same....dirty 
  
Well I do tend to clean my car twice a week. 
  
And do you tend to jack up the car twice a week to take the wheels off and clean behind the caliper where the lines sit? 
  
That's where they go? Lol. Ok so I won't get round to clean them ever.