Painting a funnel in red was a recognition signal that was applied during WW1 when ships were in home waters so that they did not become victims of friendly fire. The system of painting turret tops black with white circles was also used specifically to protect the warships from attack by German airships.The red funnels were applied around the time that they left harbour and supposed to be removed when the were clear of the coastal defences and re-installed when they neared the coast after a mission. There are signs in photographs that Seydlitz had a shabby red funnel when aground after her return from Jutland and also when crossing the North Sea for internment. A British Gunnery Officer reported that Moltke had a red funnel throughout an engagement when she was his designated target but it was the exception, rather than the rule that ships went into a surface fleet action with "Kaiser rot" funnels. I suspect that it would have been almost impossible to remove red paint at sea from an uncased funnel in a battlecruiser at high speed. After all, early Cunarders had red funnels made from red-lead pigment mixed with milk which produced a smart, permanent, heat-resisting, finish.