Customize.md

Customization

Colors can be set by modifying the  Theme.less
stylesheet or by adding to your  style.less  file.

Using the  .cursor-line  class selector is not recommended as
you will loose highlighting when selecting text on the current line.

atom-text-editor::shadow {
    
    /*
     *  Ｂａｃｋｇｒｏｕｎｄ
     *  Uses !important to override theme specific settings
     */
    
    .line.highlight-line {
        background : rgba( 255 , 0 , 0 , 0.3 ) !important ;
    }

    /*
     *  Ｕｎｄｅｒｌｉｎｅ
     *  Replace `solid` with `dashed` or `dotted` depending
     *  on the style you selected in the settings.
     */
    
    .line.highlight-line-multi-line-solid-bottom {
        border-bottom-color : red ;
    }

    /*
     *  Ｂｏｒｄｅｒｓ
     *  Style for the optional area selection borders.
     */
    
    .line.highlight-line-multi-line-solid-top {
        border-top-color : red ;
    }
}