Can't change Alpha value of Image color

I have a function that changes the Alpha value of a UI Image.

    public void ZenChangePlayButton()
        innerRingImage.color = new Color32(255, 255, 255, 255);
        outerRingImage.color = new Color32(255, 255, 0, 255);

    public void ZenUnchangePlayButton()
        innerRingImage.color = new Color32(255, 255, 255, 0);
        outerRingImage.color = new Color32(255, 0, 0, 0);

However, once I am in play mode and one of these functions are called, the RGB values change, but the alpha values don’t. Not even through the inspector (though the inspector works when out of play mode).

Is this related to my script, how the UI works, or is it just a Unity problem? Thanks for any insight.

try creating an animation to change the alpha of a image

creating animations work for me every time