Atom Editor styles to differentiate keys and values in JSON files

styles.less

// Style JSON keys and values differently
atom-text-editor::shadow .meta.structure.dictionary.json {
  // Keys
  & > .string.quoted.json,
  .punctuation.definition.string.json {
    color: @blue;
  }

  // Values
  & > .value.json > .string.json,
  .value:not(:first-child) .punctuation.definition.string.json,
  .array > .string.json .punctuation.definition.string.json {
    color: @green;
  }
}

Now an Atom Editor package: https://atom.io/packages/colorful-json.