Historical clue formulations

• Like the Danube, to Germans — 2024-09-28
• Color of the sky, in Germany — 2023-03-03
• Color of der Ozean — 2016-05-05
• Danube's color, to a Berliner — 2013-11-06
• Blue, in Bonn — 1998-06-10
• Blue in Berlin — 1994-01-30