You will be able to do this using the sprite masking extension, but you will have to duplicate your objects.
Here is how I did it with simulating silhouettes. 2D silhouette visible throw walls - #11 by Silver-Streak
You should be able to do it with text the same way (duplicate objects already in the other color).
Outside of that, you can use a layer effect to reverse the color palette of an object or entire layer, but not parts of an object (without masking).