You can use text boxes in MS Word to good effect. By turning off the repel function you can overlap text boxes to position text or symbols - set these to white, or any other colour that suits your purposes - where you want them over a "bottom" text box filled with the base colour (essentially, what I'm trying to say is that you build the signs up in layers).
Having done all that and saved them, you should print on glossy photo paper to simulate the enamel signs. Print the coloured backgrounds oversize if the colour extends to the edges, otherwise leave a white border (unprinted). If the colour extends to the edges of the signs, after you cut them out, colour in the edges with a matching felt-tip pen or paint.
I have made early BR enamel station signs in this manner and would deem them a success.
Above all, don't be afraid to experiment, you hve nothing to lose by trying out different techniques, except time.