The handle to the text object and the handle to the "square" (not sure what you mean here, it could be a rectangle object, a patch object, an axes, who knows...) both have properties that allow you to edit their colors. But the property names vary between different sets of objects. Since we don't know what kind of objects you're working with, we can only be as specific as the content offered in your question (which isn't specific).
The two most common property names that changes an object's color are
This demo below shows you how to change the "Color" property. The "FaceColor" property of other objects works in the same way.
h = text(. . .);
h.Color = 'r';
h.Color = [1 0 0];
set(h, 'Color', [1 0 0])