the MGT Spinward Marches book mentions a few outside the imperium worlds that have a explicit amber code. most of them are worlds with extra hazards similar to those that would justify the normal amber zones in the imperium.
Then, my assumption upon this information (and what is sis in othr posts is that either:
- all systems beyond Imperial space not specifically stated as Amber or Red zones are somwhere between Greeen and Amber, as not all garantes for Green systems can be assumed.
- All systems beyond Imperial space are classified as Amber Zones. Those specifically stated as such imply special dangers/limits, and are in fact somewhere between Amber and Red zones.