Why the line number background color and foreground color is not in the syntax highlighting section in Editor settings?
Because the line number background color, foreground color, margin colors should match the current color scheme so they must be a part of Syntax Highlighting (not part of Environment Colors).
Each time i change the color scheme, i should go to Environment 》Colors and change them. They must be part of the Editor 》Syntax Highlighting. I am using version 17.12.