Template vector images remaining black when animated - ios

Question

I have a UIButton initialised with a template vector image, like so:
UIImage *buttonImage = [UIImage imageNamed:#"image_0"];
self.button = [UIButton buttonWithType:UIButtonTypeCustom];
self.button.frame = CGRectMake(0, 0, buttonImage.size.width, buttonImage.size.height);
[self.button setImage:buttonImage forState:UIControlStateNormal];
self.button.tintColor = [UIColor whiteColor]; // Icon color
The template icon is coloured white by setting the buttons tint. This works like a charm! :)
When a specific action occurs, I would like the button image to animate; repeatedly cycle through three images with the following method:
- (void)startAnimating {
if (![self.button.imageView isAnimating]) {
UIImage *buttonImage1 = [UIImage imageNamed:#"image_1"];
UIImage *buttonImage2 = [UIImage imageNamed:#"image_2"];
UIImage *buttonImage3 = [UIImage imageNamed:#"image_3"];
self.button.imageView.animationImages = #[buttonImage1,buttonImage2,buttonImage3];
//self.button.imageView.tintColor = [UIColor whiteColor];
self.button.imageView.animationDuration = 1;
[self.button.imageView startAnimating];
}
}
The problem is that the animating images are all black (like the template vector images), and not white as expected.
Even with the commented line added the images remain black. Any ideas as to what I could try to do in order to keep all images white at all times?
Thank you in advance,
Anders