After closer examination I believe it is working, during play. Now I have a note definition that gives an unknown player a note when minraising his first button. After the first opportunity players get a color definition which makes these players being filtered out at subsequent hands.
But how do I make this work for my current database? In which order are note defnitions and color definitions then applied? I get way to many notes on my current database so I have the feeling that during reset/recreation of the notes it takes a while before the color definition is applied to the players after the first opportunity. So most players are getting the note also at the 2nd, 3rd, etc opportunity which shouldn't be the case.