[API] Fix inconsistent label color format (#10129)

* update and use labelColorPattern

* add TestCases

* fix lint

* # optional for templates

* fix typo

* some more

* fix lint of **master**

models/user.go

@@ -1044,7 +1044,7 @@ func ChangeUserName(u *User, newUserName string) (err error) {
 	} else if isExist {
 		return ErrUserAlreadyExist{newUserName}
 	}
-	
+
 	sess := x.NewSession()
 	defer sess.Close()
 	if err = sess.Begin(); err != nil {