Slider background-color not working

[mm-psymbl]

Using the slider and everything seems to working expect the background color (which works in the native Slider).

.slider {
    ripple-color: $c-white;
    elevation: 4;
    color: $c-orange;
    background-color: $c-white;
}

So with the above the line of the slider is orange instead of white.

Any idea why or a fix?