On monocolor printers, the fill color will be the color of the installed ribbon. For more information about printing color graphics to THT printers and printing color in Brady Workstation, see:
Printing an edge to edge fill may leave a white border (unprinted margin). Using the ribbon to print the background space is introduces increase wear to the print head. In most cases we recommend using a solid fill label material and white ribbon: Why Can't I Print to the Entire Label Area?
Method 1 - Reverse Print
Launch Custom Designer, add a text box and type text.
Select the "Reverse Color" option in the text properties.
Note: Reverse print is not an option for Text on Arc. Use No Fill to accomplish this.
Method 2 - No Fill
Open the Custom Designer App in Brady Workstation.
Create a solid-filled shape first by clicking on the Shapes & Lines icon on left menu and then select the blank label.
Select the rectangle just created and you should see the Rectangle Properties tab. In Fill Pattern field, select Solid fill (black square).
Create a Text object outside the solid-filled rectangle, enter text and use the "No fill" option for color.
Layer or move the text object on-top-of / in-front-of the filled rectangle and you are done.