[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**

templates/swagger/v1_json.tmpl

@@ -5317,6 +5317,9 @@
         "responses": {
           "201": {
             "$ref": "#/responses/Label"
+          },
+          "422": {
+            "$ref": "#/responses/validationError"
           }
         }
       }
@@ -5443,6 +5446,9 @@
         "responses": {
           "200": {
             "$ref": "#/responses/Label"
+          },
+          "422": {
+            "$ref": "#/responses/validationError"
           }
         }
       }