How to change the arrows with CSS

For the Advanced slider:

Modify the values below and paste the CSS in the custom CSS section of the review template...

.slickwprev-next:before, .slickwprev-prev:before {
font-size: 20px;
opacity: .75;
color: #ddd;
}

For the Normal slider:

It's a little more complicated, but these are the values to modify.

.wprs_unslider-arrow {
width: 28px;
height: 28px;
background: 58% 51% no-repeat rgba(0,0,0,.2);
background-image: url(imgs/slider_arrow.png);
background-size: 7px 11px;
border-radius: 32px!important;
text-indent: -999em;
opacity: .6;
}

Let me know if you are looking for something specific and I'll help you out.