You can use the backgroundColor property for this:
self.yourView.backgroundColor = [UIColor purpleColor];
Pre-defined values are
You can also define your own colours by creating a UIColor object (from RGB or HSL values). Here’s how you can create your own RGB colour and use it with the above example:
UIColor *myPurple = [[UIColor alloc]initWithRed:1 green:0.5 blue:1 alpha:1];
self.yourView.backgroundColor = myPurple;
RGB and alpha must be defined as CGFloat numbers, i.e. between 0 and 1. The alpha value is the opacity, so 1 is fully visible and 0 is invisible.