I don't know if you wanna take this route since you're talking about just an e-mail alert...but one option is to set up a profile in that person's name, like you have your other sound profiles.
Another option would be to set up a filter so any email from your boss gets sent as a Level 1 message. Then set the Level 1 alert to what you want in your profiles.
You can set up the filter right on the BB. Open Messages, press the menu key and select Options. Open Email Filters, press the menu key and pick New. Give the filter a name, scroll down to From, press the trackball, pick Select Name and pick the contact from your address book. Set the Action to Forward, then put a check in Forward with Level 1 Notification. Save it and you're done.
Since they're Level 1, they'll show up red, the same as PIN messages.
If you're getting PIN messages, they'll use the same notification.