Using Conditional Formatting as suggested in my first post and also by DatabaseMX ...
1.) Open your form in Design Mode.
2.) Select your Date_Due control.
3.) From the Menu Bar click Format --> Conditional Formatting
4.) Set the Default Formatting Font Color to Black and ensure it is Enabled by clicking the icon to the far right in the box.
4.) Set Condition 1 to ...
Field Value is Greater Than or Equal To Now()
Change the font color to red and ensure it is Enabled by clicking the icon to the far right in the box.
ET