You take an eye exam and tell everything backwards.
Example (not quite but you get the idea):
When he does:
E you do 3
3 you do E
W you do M
M you do W
The suit is given to you by Dr. Spyglass, who runs the Spyglass Eyewear store. (He is secretly a spy scientist.) (see related question)
The docks are on the left side of the island. Get the decoder from headquarters, and the chameleon suit from Spyglass Eyewear, so you can slip past the guards and dogs.
You get it from Doctor Spyglass, at Spyglass Eyewear, who secretly does research for the spy agency. (see the related question)
You can buy the "phantom" costume in the Poptropica store, but it will not work on Spy Island to get past the guards. Get the Chameleon Suit from Professor Spyglass. (see related question)
You can only wear the chameleon suit on Spy Island.
The chameleon suit.
go to Dr. spyglass's office and ask for an eye appointment. But instead of saying the right thing say the opposite of what he is pointing to. He will invite you upstairs throgh the door on the roof and there will he give you the chameleon suit.
you don't
You can slip past the guards to get to the roof, and past the guard dogs inside, if you have the "Chameleon Suit" that makes you invisible. You get it from the doctor at Spyglass Eyewear. (see the related question)
You can't reach the rooftop door to the docks, much less get past the guard dogs inside. That is, unless you have the special Chameleon Suit which renders you invisible. Get the Chameleon Suit from Dr. Spyglass at Spyglass Eyewear. (see related question) To avoid detection with the Suit, stop moving when you see an approaching guard or dog, to give yourself time to blend into the background. Once they pass, you can move again. The safe holding the First Spy has a hole in its ceiling to enter through. (see related Chameleon Suit question)
The invisible "Chameleon Suit" can be acquired at Spyglass Eyewear. Go to the store and ask for an eye test. When the doctor points at a figure, choose the one that is the opposite of it (M instead of W, E instead of backward E, etc.). He will go upstairs and you can enter from the outside door. Dr. Spyglass is working with the "good spy" agency and will give you the Chameleon Suit. Use it to get past the guards and dogs to rescue the first spy, being held prisoner at the docks left of Main Street.
you get it from the guy in spyglass eye wear. You talk to him and tell him you're a spy and he will take you upstairs. Then he will give you the camouflage suit.