As you already have a 6-line wrasse in the tank, I would not recommend another wrasse. 6-lines are usually very agressive and do not tolerate the introduction of another wrasse, especially in a small tank such as yours. Also, note that wrasse tend to be jumpers, so if you have an open top, chances are that it will only be a temporary fish.
Your tank size greatly limits the fish you have to choose from. If you want to go with a wrasse, get the 6-line out of there. For an angel, perhaps a cherub or flameback but take your chances on them nipping. Otherwise, how about a strawberry dottyback, diadema dottyback, or royal gramma. Perfect for the tank size and a ton of color.
JD