Single field type frame color can not be changed, while you can change field caption in color, size, style and etc...
You can vote or create new idea on this by http://forums.adobe.com/community/formscentral, Submit Feature Request link under Resources.
And, another quesiton.
After creating the pdf file, if input Chinese character in the text field, the Chinese character cannot show correctly.
I believe you created an English form in FormsCentral and then downloaded the PDF form to fill it out with Chinese. In this case, it's a known limitation of our product, but there is a workaround. In formscentral, you may go to Options tab and then click on Languages and Formatting, then change the language to Japanese and download a new PDF form to fill out. However there is a tradeoff, with this option, your form's date/time, messages and submit button will be in Japanese. I have submitted the issue for engineers to review and hopefully there is a better solution.