I'm trying to complete my collection of airmail booklets. I recently purchased a pair of booklets purporting to be BKC18 and BKC19. They are the bottom two of the three shown in the following image:

I have the top booklet labeled in my collection as BKC15. I've had it for some time, and never thought to question its identification before now.
All three booklets have panes with Slogan 3. The panes in the bottom booklet are clearly tagged. Hence I don't think there is any doubt about identifying it as BKC19. But I am not seeing any tagging on the middle booklet, and it should be tagged. But if it is not BKC18, what is it?
Contributing to my confusion is a confusing presentation of these booklets in Scott:

Since these booklets are all $2 with Slogan 3, that limits them to BKC14, BKC15, BKC18, and BKC19. Now I've never imagined that I have a BKC14. But I'm confused by what is meant by the italicized "
pink" in the Scott descriptions. When I bought the "BKC18" it was described as "RARE BKC18 PINKISH Booklet & a BKC19 for comparision MNH PO FRESH in EVERY WAY." Now I tend to be put off by caps and especially "rare" in all caps, but the middle booklet is clearly distinguishable as "pinkish," especially from the insides of the covers, and comparing back covers.
So is that what is meant by "
pink" in Scott. Well, if so, my "BKC15" is NOT "pinkish," but is "white," like the BKC19. But if that's what "
pink" means, then wouldn't the top booklet be BKC14? I am almost certain that it is not, and that I am confused. Or maybe Scott is wrong?
I hope I've made some sense of my confusion. It boils down to having what is supposed to be a BKC18 with no tagging, and a BKC15 that is not "
pink".
Basil