HarmonyOS stringBuilder怎么修改“发给”的字体颜色

stringBuilder怎么修改字体颜色？

getReceiverName(receiverList: DingListMember[]): string {
    let stringBuilder: StringBuilder = new StringBuilder()
    stringBuilder.append('发给：')
    console.log("receiverList", receiverList.length + "--------")
    receiverList.forEach((value: DingListMember, index: number) => {
      if (index == receiverList.length - 1) {
        stringBuilder.append(receiverList[index].name)
        stringBuilder.append('等' + receiverList.length + '人')
      } else {
        stringBuilder.append(receiverList[index].name + '、')
      }
    })
    return stringBuilder.toString()
  }