Custom animation: emphasis

I am trying to use “custom animation” in Libre Impress to emphasize certain elements in my slide.
From custom animation I choose emphasis and then there is an option of “Change Fill Color” and also “Change Line Color” but no way to choose an emphasis color.
The standard fill color selector on the toolbar is also inactivated when you’re in animation box.

P.S. I’d upload a screenshot but I don’t have enough points to upload a file.