I have my company's website address in my signature and it should be blue and underlined.
However, it shows up purple. In the editor it shows as blue and even when I recreate it, it shows up as purple again.
How can I make it stay blue?
The symptoms you are describing depend a bit on your version of Outlook and which editor you used to create the signature.
Outlook 2003 and earlier
I’m assuming that you are using Outlook 2003 or earlier. In that case, the link colors are determined by Internet Explorer as that is what Outlook 2003 and previous use to render HTML. The default color for an unvisited link is blue and the default color for a visited link is purple.
As you most likely have at least once visited the website of your company, the link color would be the “visited” color and thus purple.
Only you will see the “visited” color; the recipient won’t
However, the link color that you see, is not by definition the color the recipient will see. That would depend on the mail client that the recipient uses, the defined colors for visited and not visited links and whether or not the recipient has indeed visited your company’s website already.
Outlook 2007 and Outlook 2010
Outlook 2007 and 2010 have a similar behavior but will only show the “visited” color when the link has been visited while you click on a link and keep the message open. When you close and reopen the message, the link colors will reset to the not visited color. The same still applies; the fact that you see the visited color, does not mean that the recipient see it as well.