I don't believe it is possible to color simple text objects in Dialog System. Text objects are not generated with an object name so you cannot use the SET-COLOR function on them and using the Dialog System painter color control is ignored for text objects.

You could create a read-only entry field object and set the initial text property to the display text and then you could change the color of the foreground and background text of the entry field either statically using the Painters color control or dynamically using SET-COLOR.