I've not come across missing maps before! Unfortunate that you are the first but thank you for bringing this to my attention. I'm really sorry, but yes - as you have deduced - you have a dud copy.
I hope, like you, this is a one off. I am (sadly) in the habit of checking all the copies that I post out via eBay and I check all books at signings (I am a little OCD...) so this is the first I have come across to not have a map section. I can see how you would have been confused!
All I can advise is that you return your copy to Amazon and ask for a replacement, citing that the colour section is missing. I doubt you will be lucky enough to speak to a human over at Amazon (heaven forbid) but they are prompt with their returns policy. I had to return a DVD last week as there was no disc inside. When I went through their online returns procedure they gave me a label to print out and a box to fill in with an explanation of why. I got a response in about half an hour and another copy two days later. All turned out good in the end.
So, all I can say is sorry for the hassle and disappointment. There shouldn't be any problems exchanging it, but if there are then let me know and I'll send 'Da Boyz' round, awright?