Be careful with wrasses. They're probably my favorite and the best idea, but many are not reef safe.
Other than that you could get a chromis, indigo dottyback, tang, sleeper blue dot goby, neon goby, pipefish, Cirrhilabrus punctatus, court jester goby, jawfish...there are many others that have blue. I might get a sleeper blue dot goby. They keep your sand clear of algae and stirred. So do jawfish. Some wrasses will also stir the sand when they burrow.