There are a few other signs. Usually the snake is less active before going blue. My Ball Python goes into his moss box and doesn't come out for two weeks or so -- he sheds in there too!
Some snakes soak in water if they have a dish big enough to get into.
The blue phase lasts different lengths of time, but you should lightly mist the snake with lukewarm water from a spray bottle at least once a day during this time.
Don't feed the snake and don't handle him during this time. Feeding usually leads to regurgitation or vomiting and handling can damage the new skin forming underneath.
As Savannah said: he'll clear up and look like new but if you don't see the skin, he hasn't shed yet. Keep misting lightly and wait -- no handling or feeding! Hopefully he'll shed in one piece, but they don't always.
Be sure to check the head area of the shed skin to see if he shed the eye-caps. (They look like contact lenses.)
If he sheds in one piece, you can gently unroll the skin, measure it and subtract 20% and you have a good approximation of the length of your snake.
Sometimes the snake will eat the same day he shed, but it's an exhausting process and I usually wait till the evening after the shed to feed.
Good luck!
