Usability: Close button is barely visible on dark theme

Due to the closing button being black on very dark gray in my theme (and my poor eyesight), I am continuously closing windows by mistake when trying to activate them.

There is no option to change the close button color or its background color, or the color of the window selection bars, or to disable the closing option, or to place the close button to the left instead of the right to require more efforts/intent to really close a window, or to request confirmation on closing windows.