The image to the right shows the available color codes for signs. To use a color, prefix the code with &. For instance, to use red, you would type in "&4Red!". The bottom row is a little hard to read, but what it is showing is that you can use codes &l, &m, &n, &o for bold, strike-thru, underline, and italics respectively. These last four text decorations can be reset mid-line with "&r".