add yellow colour option for hydrant

assets/themes/hailhydrant/hailhydrant.json

@@ -52,6 +52,16 @@
             "key": "colour"
           },
           "mappings": [
+            {
+              "if": {
+                "and": [
+                  "colour=red"
+                ]
+              },
+              "then": {
+                "en": "The hydrant colour is red"
+              }
+            },
             {
               "if": {
                 "and": [