Replace with scroll bar and change color

The vertical lines that divide the calendar window with the editor, or the vertical line that divides the explorer window with the editor, by default it is purple in color when mouse is placed on it.
I want to replace the divider with scroll bar, low thickness as well as change the color, how do I go about it.

The appearance of the Primary theme is what I am trying to achieve.

Also, how do you get the horizontal scroll bar, at the bottom of the editor window?

Attached are the pictures of the vertical bars I am referring to, need to know how to remove it if possible, if not then how to change the color upon focus.

As a partial (non-css) solution, you could use the ‘Hider’ plugin

Will give it a try, thank you very much.