What colours does the state flag of Schleswig-Holstein have?

EDITORIAL LEARNING AID

Why is this answer correct?

The state flag of Schleswig-Holstein shows the colours blue, white and red. White-blue are the colours of Bavaria, white-red those of Thuringia, and green-white-red are the colours of North Rhine-Westphalia.

Blue-white-red: water, beach and brick.

This translation and explanation are editorial learning aids. The official German wording and answer key govern the examination.