slowly make gui image more transparent

In first person shooter games like Call of Duty and others, whenever you’re hurt you get a little blood-like splat on your screen and that slowly becomes transparent. Is there any simple way to do this? Or would I have to create every single image?

Use a script or Animation Editor to run the alpha on the main color of the material it uses from 1 to 0.

I answered a similar question some time ago: blood damage like call of duty? - Unity Answers