Can’t change specific widget text colour

I recently downloaded the “theme my login” plugin. I then added the TML widget to my sidebar. The text color for my widgets is currently set to white (which I want) but the text color for the TML widegt needs to be black because otherwise the username and passoword can’t be seen when typed in (beacuse the text is white and so is the box for entering the info.) I have tried changing the widget text color but this changes all of the widgets text color. How can I just change the TML widget text only?
Any help would be greatly appreciated!
Thanks in advance!