My Atom style example

atom-style.scss

atom-text-editor::shadow {
  .gutter-container {
    border-right: 1px dashed rgba(100, 120, 190, 0.2);
  }

  .gutter {
    background-color: hsl(220, 13%, 17%);
  }

  [gutter-name=linter] {
    font-size: 0.1em;
  }

  .linter-gutter {
    opacity: 0.75;
    border-radius: 0;
    left: 0;
    height: 100% !important;
  }

  div.line {
    padding-left: 0.5em;
  }
}