static parseSsaColor_(colorString) {
    // The SSA V4+ color can be represented in hex (&HAABBGGRR) or in decimal
    // format (byte order AABBGGRR) and in both cases the alpha channel's
    // value needs to be inverted as in case of SSA the 0xFF alpha value means
    // transparent and 0x00 means opaque
    /** @type {number} */
    const abgr = parseInt(colorString.replace('&H', ''), 16);
    if (abgr >= 0) {
      const a = ((abgr >> 24) & 0xFF) ^ 0xFF; // Flip alpha.
      const alpha = a / 255;
      const b = (abgr >> 16) & 0xFF;
      const g = (abgr >> 8) & 0xFF;
      const r = abgr & 0xff;
      return 'rgba(' + r + ',' + g + ',' + b + ',' + alpha + ')';
    }
    return null;
  }
Parses a SSA color .

@param {string} colorString
@return {?string}
@private