UIImage doesn't have a tint colour. UIImageView does. This little method returns a UIImage, tinted with a UIColor. It's useful for things like table icons, where the image view is read only. Means you don't have to create loads of PNGs in different colours.

gistfile1.m

-(UIImage *)imageWithTint:(UIImage *)image andTintColor:(UIColor *)tintColor {
	UIImage *imageNew = [image imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
	UIImageView *imageView = [[UIImageView alloc] initWithImage:imageNew];
	imageView.tintColor = tintColor;
	
	UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, NO, 0.0);
	[imageView.layer renderInContext:UIGraphicsGetCurrentContext()];
	UIImage *tintedImage = UIGraphicsGetImageFromCurrentImageContext();
	UIGraphicsEndImageContext();
	
	return tintedImage;
}

Swift 4:

extension UIImage {
  func tinted(color: UIColor) -> UIImage? {
    let image = self.withRenderingMode(.alwaysTemplate)
    let imageView = UIImageView(image: image)
    imageView.tintColor = color
    
    UIGraphicsBeginImageContext(image.size)
    if let context = UIGraphicsGetCurrentContext() {
      imageView.layer.render(in: context)
      let tintedImage = UIGraphicsGetImageFromCurrentImageContext()
      UIGraphicsEndImageContext()
      return tintedImage
    } else {
      return self
    }
  }
}

Improving @qubblr 's answer - using UIGraphicsBeginImageContext uses default scale factor of 1.0 and thus images can appear blurry on most phones.
Added UIGraphicsBeginImageContextWithOptions with scale factor of 0.0, which sets the scale factor to be equal to the device’s main screen.

Swift 5.1

extension UIImage {
    func tinted(color: UIColor) -> UIImage? {
        let image = withRenderingMode(.alwaysTemplate)
        let imageView = UIImageView(image: image)
        imageView.tintColor = color

        UIGraphicsBeginImageContextWithOptions(image.size, false, 0.0)
        if let context = UIGraphicsGetCurrentContext() {
            imageView.layer.render(in: context)
            let tintedImage = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()
            return tintedImage
        } else {
            return self
        }
    }
}