Закат - sunset, so "закатное золото" - a derivative expression meaning "gold of sunset" or "sunset gold", not "western gold". The author claims the color of sunset is gold.
Окон - just a pure genitive, has nothing to do with partitive: "закатное золото окон" = "sunset gold of windows". It is a poetic expression, it should be understood figuratively. It is something like "golden color of windows in the rays of sunset".

(Ты) одаришь меня закатным золотом окон - roughly "You will enrich me with the sunset gold of windows."