redux-devtools/packages/redux-devtools-log-monitor/src/brighten.ts

export default function (hexColor: string, lightness: number) {
  let hex = String(hexColor).replace(/[^0-9a-f]/gi, '');
  if (hex.length < 6) {
    hex = hex.replace(/(.)/g, '$1$1');
  }
  const lum = lightness || 0;

  let rgb = '#';
  let c;
  for (let i = 0; i < 3; ++i) {
    c = parseInt(hex.substr(i * 2, 2), 16);
    c = Math.round(Math.min(Math.max(0, c + c * lum), 255)).toString(16);
    rgb += ('00' + c).substr(c.length);
  }
  return rgb;
}