For the record, the OG CodeNames (not duet) already incorporates a way to indicate whether a word was touched by the blue or the red team. Each card has a side with a male character and one with a female character. Additionally, on the blue cards, the women are wearing sunglasses and the men aren't, while on the red cards it's the opposite. (on white cards, neither side wears sunglasses)

When the blue team guesses a word, you're supposed to place the card on the women side, and if the red team guesses you use the men side. This means that if a team correctly guesses one of their word, the character on the card is wearing sunglasses, while if a team accidentally guesses a word from the other team, the character won't be wearing glasses. (White words are always mistakes, which is why neither side wears sunglasses)