We just bought a double Coleman. It's fab. Have you tried yours yet? According to the instructions you can discard the red plugs as they are for shipping purposes.
We just bought a ColemanDouble and used it for 5 days it even withstood the kids bouncing and fighting on it and it didn't go down at all. Everyone elses needed blowing up again every night. Result!
Yep, you just bin the red bits, they are just for transit.
One question; our old Coleman Comfort has yellow valves, yet a new one we have recently bought from ebay has all black valves. Have they changed them, or have we been sold a duffer?