The answer is a pair of words.
3 Answers
The answer is:
GOLD LEAF
The trick is:
Each train car represents a letter. Each color is a bit. Red = 1, Gray = 2, Black = 4, Blue = 8. When you sum up the colors you get a number, which is the position of the letter in the alphabet. So, [7,15,12,4] = GOLD, and [12,5,1,6] = LEAF
GOLD LEAF Red = 1 Grey = 2 Black = 4 Blue = 8 Add the colors to get the alphabet.
GOLD LEAF Trick is: Each block have different color squares: Blue = 8 Grey = 2 Red = 1 Black = 4