For those confused by srbs (((comment))), this thread is requesting line-number highlighting, a visible display feature that may compliment/integrate with (((active cursor highlighting)))
2019-Jan-09 exist !!! obfuscate display information and disorganize display behavior
2019-Jan-01 better but not exist !!! better, color selection, color cursor location, for line number display.
Assuming Sublime gets serious about coloring Gutter numbers, then a first challenge for groups and projects might be Gutter Number color differentiation for teams/projects. I am sure there could be other functionality as well, such as color per syntax in overview/synch ops. And colored-number hover, popup with preferences for selected content. Perhaps even right-click line-number-color. Sky's the limit... or just simple, ready for implementation selection and cursor colors for Gutter Numbers.
Not withstanding, exist background highlight is not easy to see... Any HACKS or HOPEFULS ? Or please tell me you've been staring at it for decades, so why don't you customize colors of your selected and active line numbers?