Acrobat Pro - Transparent Button

Hi

I inseted a button, and I set the appearance for the fill and stroke to zero "no color", and linked it to a sound so user click to listen.

It works on desktop perfectly, but when open using pdf reader app on iphone, the transparent appeas as purple  transparent button when click it.

I use PDF Expert,

It is the only app I found can open pdf and play embeded sound.

If you have another reader works better on mobile, please share.

If you have idea how to hide the purple color of the transparent button, please share.

thanks