Thank you for your advice. The manufacturer gives the following official specifications regarding battery life, which are independent of the colour variant. The specifications are therefore not wrong, but it depends on whether the ANC is activated and other factors such as the volume play a role.

With noise cancellation deactivated, the playback time of the headphones is up to 11 hours. When using the charging case, the total playback time is up to 31 hours.

With active noise cancellation, the playback time with the headphones is up to 7 hours and the total playback time when using the charging case is up to 20 hours.