Dear Qian,
Please follow steps:
1. Open file CuteSoft_Client\CuteEditor\Scripts\Constant.js
2. You can find line:
editorconstant._editorSourceStyle = "background:#ffffff;margin:0;padding:0;color:black;text-align:left;";
change it to:
editorconstant._editorSourceStyle = "background:#ffffff;margin:0;padding:0;color:black;text-align:left;color:red;";
3. Test it again.
Thank you for asking