Testimonial SLider Compact with Arrows – arrow color setting

Dear support team,

On the page https://www.elianafe.com/buecher-neu5/ we wanted at the bottom of the page: from the visual representation a Testimonial Slider (Compact), but this should also be operated manually using arrows in addition to the automatic run be. see screenshot: http://elianafe.com/support/Books/Testimonial.png
Based on an existing post in your forum (https://kriesi.at/support/topic/testimonial-slider-tweak/) I have already managed to make the arrows in this testimonial slider visible.

I just don’t get the color settings. I could still define the arrow color well using css. But even if I tried to change the background of the box around the arrow to white – also via css – it only turns gray.
I just want to show the arrows without any background.

I have integrated the following code in the css:
# top.page-id-7983. quote .avia-slideshow-arrows a {
height: 80;
width: 15px;
line-height: 32px;
margin: -30px -30px 0; / * Added this * /
background: #ffffff;
color: http://elianafe.com/support/Books/Testimonial.png
}

What’s the mistake? What would you recommend?

Thank you very much and best regards Diana