Snap , Crackle, Pop!
If you hear Snap your sign may be falling off the wall. If you hear Crackle you may have an electrical short. But you definitely want your sign to Pop. Outlining your letters is a good way to get Pop out of your sign.
Outlining is when you background your letters or numbers with a color to enhance the impact of the sign. Many signs use only the color of the letter or number in the sign giving the sign a one dimensional look. By outlining the image you give the sign an added dimension that makes the letters seem to jump off the building or sign.
There are many methods and styles of outline available. These are limited only by your imagination. 
There is the letter outlined by contrasting color, i.e., black with white outline, or green with yellow outline.
You can add another aspect to outlining your letters by edging the outline itself with another color. For instance let’s say you want your letters in white with red outline, by adding a black edging the red will stand out even more.
Another look would be to run your letters closer so the outline actually merges together to give the look of 
continuity with the background.
Another way to enhance the sign even more would be to incorporate back lighting. This will not only make the letters more visible but will make the whole sign appear to float way from the structure.
Only your imagination determines what you want in a sign. Look around, see what is out there. Ask yourself, “Why did I notice that sign?” Take what you find, incorporate all the good elements into your creativity and let us help you design that sign that is perfect for you.
