Does Postgres support stored column labels that can be queried?
You might be refereing to catalog level comments, which can be used to get a description of any table and or column in the database.

Those are created using:

COMMENT ON TABLE yourtable IS 'A good description';
COMMENT ON COLUMN yourtable.yourcolumn IS 'Column desc';


To query those, you can use this kind of query:

SELECT c.table_schema,c.table_name,c.column_name,pgd.description
FROM pg_catalog.pg_statio_all_tables as st
inner join pg_catalog.pg_description pgd on (pgd.objoid=st.relid)
inner join information_schema.columns c on (pgd.objsubid=c.ordinal_position
and  c.table_schema=st.schemaname and c.table_name=st.relname)
where table_name = 'yourtablename'


Beware however that this cannot be localized.