change color schema of facebook fb:login-button

I am using facebook social plugin fb:login (new version) and here is my code.

<fb:login-button show-faces="true" perms="email,user_birthday,status_update,publish_stream"></fb:login-button>

I have a dark back ground in my page, so when user is logged on I can’t see user name as text is dark. So how do i set text color to be white? Thanks so much.开发者_StackOverflow中文版

---

<fb:login-button show-faces="true" perms="email,user_birthday,status_update,publish_stream" data-colorscheme="dark"></fb:login-button>

You can simply use data-colorscheme="dark" as with the Like button (undocumented option)