Thank you so far for the comments.

So I should receive BCs on empty addresses only. Ok

But why are there yellow AND green empty bitcoin addresses?

As far as I understand if I send some 0.02 BC from an address in my Electrum Wallet containing 0.05 BC then Electrum
- sends 0.02 to the given target address of the recipient
- creates automatically a new empty address
- send the remaining change of 0.03 BC to this new address
- add the new, just created address automatically to the list of yellow change addresses visible on the "Adresses" tab.

So why are there empty yellow addresses listed on "Addresses" Tab?

Peter