What colours does the state flag of Baden-Württemberg have?

EDITORIAL LEARNING AID

Why is this answer correct?

The state flag of Baden-Württemberg is black and gold and thus takes up the colours of the state coat of arms. Blue-white-red is the flag of Schleswig-Holstein, white-blue the flag of Bavaria and green-white-red the flag of North Rhine-Westphalia.

Black and gold like the coat of arms: Baden-Württemberg.

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