Where is the gift?
Exactly one of the red, blue, and gold boxes contains a gift. Each has a sign. Exactly one of the three statements is true and the other two are false. The colors are only labels, not extra clues.
The three signs
The red sign says, “The gift is in the blue box.” The blue sign says, “The gift is not in the blue box.” The gold sign says, “The gift is not in the red box.” Choose the box containing the gift, not the box with the true sign.
Test each possibility
Assume the gift is in each box in turn and mark every statement true or false. Do not stop at a statement that sounds plausible. Count the true statements under each assumption; the valid case has exactly one.