docs: function _retrieveColor(palette, color, hue = '500', format) {
      if (typeof palette !== 'string' || typeof color !== 'string' || typeof hue !== 'string' || typeof format !== 'string') {
          throw new TypeError('Expected a string');
      }
  
      let hexColor;
      let result;
  
      try {
          hexColor = (palette === 'md') ? colors[palette][color][hue].hex : colors[palette][color];
  
          switch (format) {
              case 'rgb':
                  result = _toRGB(hexColor);
                  result = `rgb(${result.r}, ${result.g}, ${result.b})`;
                  break;
              case 'hex':
                  result = `#${hexColor}`;
                  break;
              case 'raw':
                  result = _toRGB(hexColor);
                  result.hex = hexColor;
                  break;
              default:
          }
      } catch (err) {
          throw new RangeError('No matching color.');
      }
      return result;
  }