If you want to keep the original colors of the image, you have to do it in code:
[button setImage:[[UIImage imageNamed:@"imageName.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] forState:UIControlStateNormal];
If you want to overwrite the tint color of your button (e.g.: orange only) you can achieve that inside your storyboard. Just set the tint
color of your Bar Button Item
inside Xcode's Attributes Inspector
to the desired color: