Read/Set the text background color for the specified window.
The background color defaults to [0,0,0,0], i.e., a fully transparent black.
This means that the background is invisible. You'll need to assign at least a
non-zero alpha-value for the background to be drawn. With some text renderers
you'll also need to enable user-controlled text alpha-blending via a call to
Screen('
Preference', '
TextAlphaBlending', 1); for text background to be drawn.