My playgroup and I are a little confused on this part of the rules. Say the piles are as below:
I have a Green-3, but only know the number. Before playing it, do I announce "I'm playing this in the green pile" and check if it works, or do I show the 3, see that it is Green, and put it there?
It makes sense you'd select a pile before playing the card, else it's too ambiguous and easy to stack piles. If the card is green, it goes on the green pile, but if it was red, it also goes in a pile.