Don't worry about it. Even if he was blue on Sunday, it still might take him a few days. With both my snakes, I notice their eyes go milky and they're very pale, and sometimes they don't shed for another week. That's what my corn did last time he shed, about a month ago. I've never had any problems with my corn shedding, it's always one piece but IF you've had humidity problems or anything, try soaking your snake, or let him crawl through a damp washcloth...other than that, try not to handle him too much.
Also, don't feed him. I don't know about anyone else's corns, but mine regurged twice, because I fed him during his shed (I wasn't aware he was going to, but I found out a few days later when I found the skin). Hope this helps.
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0.1 ball python (Kilimanjaro)
1.0 amel corn snake (Houdini)
0.0.1 leopard gecko (Charlie)
1.1 cats (Kitty & Milo)
0.1 mouse (Creepers)