**Do you want to request a *feature* or report a *bug*?**
This is an accessibility issue with the new documentation website.

It's a clear-cut problem, but the solution is pretty open ended and ill defined. Might be difficult, and could use some design creativity.

**What is the current behavior?**
We are using [Prism.js](http://prismjs.com/) for the syntax highlighting styles of our code snippets. We also sometimes want to "highlight" a certain line, so we lighten the background of that line. With the lighter background, many of the font colors don't provide enough contrast.

**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://jsfiddle.net or similar (template: https://jsfiddle.net/ebsrpraL/).**

You can verify this by [running the aXe a11y audit](https://www.deque.com/products/axe/) on this page: https://reactjs.org/docs/introducing-jsx.html

**What is the expected behavior?**

We need a way to highlight a line without losing so much contrast.

BUT choosing a different hue without making it lighter looks bad in my opinion, and I would rather not fiddle with the various font colors used in the syntax highlighting.

We should either collaborate with the Prism project to add a 'highlight' option with enough contrast, or find another library/system to use for syntax highlighting.

/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @emails react-core
*/
'use strict';
import {css} from 'glamor';
import {colors} from 'theme';
const prismColors = {
  char: '#D8DEE9',
  comment: '#999999',
  keyword: '#c5a5c5',
  lineHighlight: '#393d45',
  primitive: '#5a9bcf',
  string: '#8dc891',
  variable: '#d7deea',
  boolean: '#ff8b50',
  punctuation: '#5FB3B3',
  tag: '#fc929e',
  function: '#79b6f2',
  className: '#FAC863',
  method: '#6699CC',
  operator: '#fc929e',
};
css.global('.gatsby-highlight', {