Data sheet says....

Mixed mode : the device is line locked to the
incoming CVBS signal. The text is superimposed
over the CVBS input either in B&W or translucent.
It may also be superimposed in color by using the
R/G/B outputs.

As it stands it switches to white characters on the incoming video.

I have not got a good red out of it, by playing with tint/color/contrast and brightness. If you did manage to get a decent red, that of course would impact on the color of the incoming video signals.

A black background MAY look better instead of blue, - the eye/brain can do funny things with colors.