Winterizing! this is CrAzy! Antifreeze blow out...

Hey that sounds like me last year!!
Like others have said the check valve isn't seating right. I simply put a plastic plug in the hose fitting and used that all year. When I winterized this year it had reseated itself, and I had to push in on the check valve to get the pink to come out.
Hope the same works for you.
Brian