Preparing, cooking and picking a live blue crab.

Wish I could transmit drawings, cuz that's the easiest way to show you what to do and where the meat is.

Blue crabs are usually cooked before the meat is removed, with steaming probably the most common method. Once they're cooked (the shells will turn red), let them cool down.

Turn the crab over and remove the apron. From you description you happened to have gotten all males (the female aprons are more triangular). Break off the apron and pop the top shell. What you'll see is a batch of long, thin "fingers," plus the innards. Discard all of that by pulling the fingers away, and giving the rest a quick rinse under running water. 

Break the body in half, front to back. Now turn a half-body towards you so that you're looking at the sidewall along the break. What you'll see is a series of cells, or compartments. The meat is contained inside those cells, and has to be picked out, be careful not to get cartiledge mixed in. There are picks made specifically for this purpose, but even a wooden skewer will work.

I have no idea what the greenish/brownish coloring was on the claw meat. Crab meat is, essentially, white. The claw meat has some of the blue coloring of the claw shell, but that the only color that should show.

For future reference, if you buy seafood you're unfamiliar with, ask the fishmonger to show you how to clean and prep it. I've never known one to refuse such a request.

For a step-by-step pictorial of how to clean crabs, along with some great recipes, try here:

http://www.the-outdoor-sports-advisor.com/crab-recipe.html

Buy canned crab :)

But seriously, all of what KYH said.  Couple of years ago I had some monster sized crabs caught in  the mangrove groves in the Northern Territory of Australia, given to me by a friend.

As they were so big, getting the meat out was quite easy.  A hammer was needed. As for the size of them, I could fit only one at a time, just, in a dutch oven,  Cooked ém, cracked ém, had a lovely feast complete with a garlic butter.

Re the greenish/browning on the claws ....just a thought, maybe it was preparing to shed its shell.  No info on that really.

Bigger is always better if you can find them.

5" point-to-point along the shell is the minimum size blue crab can be kept. And they're so popular that that's the most common size you'll likely find in the markets.

Catching your own is both fun and easy, and you might give that a try. There are traps and nets used for that purpose---available at most tackle shops in crab country. Or you can just use a weighted string, some bait, and a dip net. That's the most fun way to do it, but the others are more productive.

I cooked and picked a dozen my grandson caught for me yesterday, with the corn and potatoes.  They were, as usual, fantastic to eat but a very labor intensive meal.  KYH's explanation on the picking process was excellent.  You just have to pick a bunch of them to get the process down, and you will certainly understand why the crabmeat you purchase is so expensive.

We boil our crabs whole with some crab boil, lemons, and a touch of white vinegar.  Crabs vary greatly as to the amount of meat in them.  When you buy the live crabs you want to choose the ones that feel the heaviest.  We catch all of ours, and it seems there is some cycle, possibly moon phase related, when all of your crabs are packed with meat - or not.

My cajun friend had a crab boil recently, and his crabs were cooked perfectly.  He doesn't time the boiling time..  He cooks them until he notices some "fat" releasing from the crabs, and then lets them steep with the fire off for five minutes. The batch I cooked yesterday took over ten minutes boiling time.   I can tell you that the six minutes you cooked them was not long enough. 

The crab claw meat is browner, and somewhat nutty tasting.  I actually prefer it when preparing stuffing for flounder and for some sauces. It is some pretty wonderful stuff after you get the meat out of the shell and on your plate.