How to change color of side arrows in testimonial?

In formatting the PageBuilder CK module "Testimonials" I was not able to find any option on how to change the color of the 2 side arrows (used to move around the various testimonials).
Because a dark background is needed in my testimonials, the already dark arrows become almost invisible.

How to change their color to white/gray?

Hi
the arrows are show using an image :
/plugins/pagebuilderck/testimonials/assets/images/prev.png

you shall replace this image, or override the css rule to put your own image
.pbck_testimonials_controls .control_prev { code here ... }
and
.pbck_testimonials_controls .control_next { code here ... }

CEd

I was able to get the result by changing the PNG image as you wrote in your first suggestion.
I would not be able to comply to your second suggestion, not having enough knowledge to do that.

Thank you!