In FCOM they say that triangle becomes amber when RAM AIR flap is not fully open, and both pack flow control valves are closed.
Here the RAM air flap is emergency ram air or RAM Air flap for the Packs?
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It refers to the valve controlled by the guarded RAM AIR pushbutton referred to as "emergency RAM air" in the system diagram.
When the triangles (think of them as arrows indicating flow) are white the triangles indicate sufficient flow of air for conditioning/pressurisation.
The normal position of the guarded Ram Air pushbutton is 'off', ie no light illuminated.
In case both packs fail/shutdown, i.e. both the pack valves are closed, the remaining source for getting airflow through this system is the RAM air. If that is not fully open, while the pack valves are both closed there is insufficient airflow and the triangles therefore turn amber.