Red or blue?

What do people do who are in love but do not yet live together? They send letters or a card. What did people do in former Czechoslovakia if they wanted the letter to be personally delivered to their loved one by the postal carrier? They would affix an extra stamp next to the postage stamps to cover the delivery fee.

On March 1, 1937, the Czech Post issued two stamps to cover the delivery fee. A red stamp of 50 heller (halé??) could be affixed if the sender of the letter desired that the letter be personally handed over by the postal carrier. The sender received no confirmation from the postal carrier regarding this personal handover!

The second stamp was blue. This stamp was intended for senders of letters who were not 'rich' enough to purchase the red stamp. If one still wanted the postman to deliver the letter personally to the addressee, one could indicate this. The blue stamp would then be affixed by the postal service itself. The addressee then had to pay 50 heller. A kind of stamp, then. But what about the green stamp impressions? In Germany and other countries, Stamp Day was celebrated on January 10, 1937. The name of the city, Aussig, appears in the stamp. The name of the city is also written in Czech. That means Aussig on the Elbe. The city lies between Dresden in Germany and Prague at the foot of the Ore Mountains in North Bohemia. Many German-speaking people lived here, also known as Sudeten Germans, hence the German text. I have no explanation for the date of February 14, 1937, on the stamp. Why two weeks before the issue date? Back to the letter with the blue stamp. What to do if the addressee refused the letter, and thus did not want to pay? Then the letter went back to the sender, who then had to pay the amount after all. Is this perhaps where the saying comes from that the sender "got the blue"?