Cannot remove fill color in Appearance - Button Properties

[acrobat_mru]

With previous versions of Acrobat, we could remove completely (transparent background) the Fill Color in the Button Properties. It appears that we cannot anymore in Acrobat DC as it defaults to a white background?

Any solutions or hidden features to remove the fill color completely (transparency)?

[Kanikas]

Moving to Installing, Updating, & Subscribing to Acrobat​

[novovos · Accepted solution]

I figured out a work-around for this issue in Acrobat Pro DC.  Open another pdf that you've already marked up with a transparent rectangle (or whatever shape). Right click and then select "Make current Properties Default".  It will now be transparent in any pdf you are marking up.

[Tobbe_]

Is this a bug or did Adobe do this on purpose?