CBP secondary screening codes
 

I had the misfortune once to say that not everything belongs to me in my baggage (wife's clothes) = automatic secondary every time + denied GE. I usually enter from YYZ bimonthly and they just put my passport and card in a yellow folder. While at other POE the codes vary, there's usually an S ( for secondary I assume).
Canadians use different codes every time.

I dont think there are official codes - what they write depends on the local airport. Sometimes they write 1 or 2 - turned out to be inspection rooms in that particular airport. If they write anything - you bet you are being send to secondary! The leave notes in the computer for the next person to read and the "codes" really mean nothing.

What are the different color folders? I’m going to guess that the green one is for agricultural inspection? What are the yellow and red ones for? More serious things?