Brother GTX600NB - Specify Whether or Not to Use the Background Black Color

4-31
Creating print data
4-4-7. Specify whether or not to use the background black color
If you have selected [Color+White Ink] in the [Select Ink:], the setup items of [Use background black color (for black
T-shirts only)] will appear.
In the event that you wish to print a black T-shirt making use of the T-shirt's background black color, mark the [Use
background black color (for black T-shirts only)] checkbox.