It wasn't the case from the beginning of the epidemic, but Queen Mathilde made a specific effort to wear a mouth mask that matches her clothing in public outings. This could be seen on 16 June, when she visited the "Van Eyck in Bruges" exhibition in the Groeningemuseum in Bruges (photo above).
"Safety and Style! Queen Mathilde of Belgium masterfully coordinates her face mask with her outfit", America's People Magazine wrote earlier. They were talking of "an upgrade" compared to earlier outings where she was still wearing a normal mouth mask. (bottom photo)
The photo below shows Mathilde's visit to a flower farm at the end of May, when she met floriculture entrepreneurs at Gediflora in Oostnieuwkerke.