A DUET RIDDLE

mel

Alright, so let's see!

Just read through the riddle and think that it is a pretty nice one!

Moreover I think that the cities looked for are Venice, Istanbul and Rome -

BUT:
looking at the thingy the letters are supposed to be set in...
confusion about the red field... "R" or "s" probably only one goes

or is it just a tricky construction this time and two letters maybe share a colour?

Anyway, there'll be a solution for it...