How do I change the color of a button in a Power App

Question

Among the available templates to use to start generating Power Apps is one entitled "Power Apps Training",  This looks like a tool were someone can learn Power Apps in a psudo-tutoral where you just press F5 to switch from preview mode to editing mode.  It has instructions and exercises included.

The problem is on the page L06_Rules

On this page, there is a slider along with a button like this:

To best explain what is happening, I will post a screen shot of the instruction:

 Before I forget I will mention that there is a typo.  There are ony 4 steps.  The number that comes after three is four, not six.

But that is not the issue I am having.  Although I am able to complete the task of changing the text of the button according to the number on the slide control.  I can not get the color to change.

What happens is when I click on the button for modification, I am able to select the Fill option from the top left of the development environment and add this.

And, by the way, it seemed to only accept me typing "Color.Red" instead of "Red" but it adjusted the display to be just "Red". But, still, when I press the F5 button to run, no color is changed on the button.

Please advise and help.