As a UX designer I have encountered situations where UX recommendations were followed in terms of layout, functionality and interaction design. However when it comes to the details of the design itself I have had to weigh my recommendations very carefully to avoid:

1. Limiting designer creativity.

2. Being perceived as impeding on someone else professional territory.

Typically I would suggest further recomendations when there is lack of affordance or when the final designs/visuals are likely to hinder accessibility.

So as stated above, my question is:
How far should a UX designer venture in graphic design territory without being perceived as limiting creativity or impeding on someone else professional territory?

Context:

The obvious answer would be to clearly explain how the design affects usability and user experience as whole but my question specifically relates to situations where this approach has failed or engendered so much discussion and controversy that it wasn’t worth the effort.

So far I have been focused on enriching my recommendations with guidelines and detailed explanations but this is time-consuming and focuses too much on creating documentation rather than getting the job done.