Change Color of Slider Bar from Gray to Color Gradient

Hello,
I am trying to change the background color of the slider bar (Draggable Sliders) to a color gradient going from red to yellow to green. I found the following post <https://www.qualtrics.com/community/discussion/2269/color-transition-in-slider-bar> which addresses my question and used the following custom css from that link:
.Skin .horizontalbar .Slider .track {
background-image: linear-gradient(-90deg,red,yellow,green);
}
Once the css has been added the slider bars disappear (see included image) instead of the intended color gradient.
I also tried the following javascript but had similar results.
var that=this.questionId;
jQuery(".track:eq(0)").css({ "background-image":"linear-gradient(-90deg,red,yellow,green)"});
Does anyone know why this might be happening and how to rectify the issue?