Slider bar issues

Hi. There are a few posts on sliders but couldn’t find the answer I was after.
I was just hoping to clarify something. Attached is an image that shows under the “Appearance” tab the “Slider handle color” is white.
I haven’t included this but a bit further down there is a “Style” tab with subheadings related to the bar and subheadings related to the “thumb” ie Normal thumb image, Hovered thumb image, Disabled thumb image.

I just wasn’t sure what the “Slider handle color” refers to - i’m assuming the “thumb” is the little box that can be moved.

And one other thing I noticed is that when using an image for the thumb the actual bar shortens a little bit at both ends.