First off I want to say I saw a couple of posts on this site about how to do this, although none seemed to work for me so please don\'t close this down until I get it working.>
As UISlider implements the UIAppearence protocol you can set its background color like:
mySlider.backgroundColor = [UIColor lightGrayColor]; // Or any other color
or:
[[mySlider appearance] setBackgroundColor:[UIColor lightGrayColor]];