This may happen because of customizations made to your CSS in Page Designer. You'll need to take the below steps to change the text color to black again so that it can be seen against a white background.
  1. Go to Web > Page Designer
  2. Click Next to get to the Colors and Styles tab
  3. Click Advance Colors and Styles > Edit Style sheet
  4. Paste this code:

This section displays the basic styles that you edit from the page designer. You can edit the classes directly to further customize your web pages.

.BBFieldCaption, .BBDivFieldCaption{

/***** End basic styles  *****/

Click Save