I've looked at a few other tickets related to this query but couldn't figure out how to change the actual color of the "is-selected" class font color. Here's what I've got:

.testimonial_slider[data-style*="multiple_visible"] blockquote {
    color: #6b6b6b !important;
}
.testimonial_slider[data-style*="multiple_visible"] blockquote p~span {
    color: black !important;
}

.testimonial_slider[data-style*="multiple_visible"] blockquote.is-selected {
    color: #6b6b6b !important;
}

The initial two tweaks work, but the third doesn't change the font color. As it is, the white is hard to read on the accent-color background. So I'd like to be able to manipulate the color to a darker hue.

Thanks!