Liar's Paradox - Labyrinth

Top Red Guard: “You can’t ask us. You can only ask one of us.”
Top Blue Guard: “It’s in the rules, and I should warn you that one of us always tells the truth, and one of us always lies. That’s a rule too.” Gesturing to the TRG, “He always lies!”
TRG: “I do not! I tell the truth!”
TBG: “Oh, what a lie!”

(via/completed @ Life's Paradox)