What are the colours of the state flag of Saarland?

EDITORIAL LEARNING AID

Why is this answer correct?

The flag of Saarland has been black-red-gold since 1957 and shows the state coat of arms in the centre. White-blue is the flag of Bavaria, black-yellow the flag of Baden-Württemberg and green-white-red the flag of North Rhine-Westphalia.

Saarland: black-red-gold with coat of arms, since 1957.

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