Jeff

Blue: Both of these statements are true. The gems are in this box.

White: The gems are not in the blue box. The gems are not in the black box.

Black: The gems are in a box with a false statement. Both statements on the blue box are true.

A: white

I guessed blue but was wrong.

Blue: The statements on this box are either both true or both false. This box is empty.

White: This box is white.

Black: All statements on the blue box are true. The box with no false statements has the gems.

A: Black

Blue: The gems are not in the black box.

White: This statement is as true as the statement on the black box.

Black: The gems are in the white box.

A: White

Blue: This is not an empty box. The gems are not in the black box.

White: This statement is true. The above statement is false.

Black: The gems are in the black box. The gems are in the white box.

A: Blue

Blue: The top statement on the white box is true. The gems are not in this box.

White: exactly two statements with the word 'true' are false. The gems are not in this box.

Black: both statements on the white box are true. Both statements on this box are true.

A: white