各种UIColor颜色的设置
UIColor blackColor
UIColor darkGrayColor
UIColor lightGrayColor
UIColor whiteColor
UIColor grayColor
UIColor redColor
UIColor greenColor
UIColor blueColor
UIColor cyanColor
UIColor yellowColor
UIColor magentaColor
UIColor orangeColor
UIColor purpleColor
UIColor brownColor
UIColor clearColor
UIColor lightTextColor
UIColor darkTextColor
UIColor groupTableViewBackgroundColor
UIColor viewFlipsideBackgroundColor
UIColor scrollViewTexturedBackgroundColor
UIColor underPageBackgroundColor