update gitlab label's color (#9010)

* update gitlab label's color

fail if both new_name and color are missing, as per Gitlab API docs.

* add changelog

* Update changelog with suggestion

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

* remove unneeded check

* Update changelog

---------

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

changelogs/fragments/9010-edit-gitlab-label-color.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - gitlab_label - update label's color (https://github.com/ansible-collections/community.general/pull/9010).

plugins/modules/gitlab_label.py

@@ -275,6 +275,8 @@ class GitlabLabels(object):
             _label.description = var_obj.get('description')
         if var_obj.get('priority') is not None:
             _label.priority = var_obj.get('priority')
+        if var_obj.get('color') is not None:
+            _label.color = var_obj.get('color')
 
         # save returns None
         _label.save()