Everybody Wins!

Three different coloured cloth covers hide three tumblers from view. Two spectators are invited to play. Each spectator choose a colour, you are left with one. Spectators can change with each other and with you. When they are completely satisfied, the covers are removed.  

They both get a gift to drink your health. 

But what a pity they didn't choose the one colour remaining, for when the cover is removed, that tumbler is see to be filled with 10 Pfund or 50 Pfund Noted