code: function _getNextColorPair() {
    const indexPair = [colorPairIndex];
  
    if (colorPairIndex < distinctColors.length - 1) {
      colorPairIndex++;
      indexPair.push(colorPairIndex);
    } else {
      colorPairIndex = 0;
      indexPair.push(colorPairIndex);
    }
  
    return indexPair;
  }
docs: _getNextColorPair - returns the next pair of indicies to interpolate between.
  
  @private
  
  @returns {Array} An array containing the two indicies.