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Mocha looks like a typical shelter Pit Bull mix. There's really no way to know what she is, since she's adopted and you don't know her parents lineage. Of the breeds (APBT, Amstaff, SBT and Ambully) that fall under the umbrella term "Pit Bull" I think she's going to look most like an Amstaff or a Bully type. (Ambully and American Bulldogs are different...Ambullies are the ones that are typically short and stocky)
I think the shelter misinformed you on her color...maybe it's the lighting of the picture though. She doesn't look blue at all to me. She looks like a light redish color, which I think is refered to as liliac. This is a link to a thread that contains a video of one of our forum member's dog-Veronica. Your dog looks to be the same color as Miss V. viewtopic.php?f=4&t=154596
***Actually I did a little bit of research and technically, if your dog is liliac then she does have blue undertones. See here: viewtopic.php?f=2&t=144748&p=1907704&hilit=+color#p1907704
Have you guys ever owned a PB type dog before? If not, are you familiar with their backgroud-the fighting? Even though your dog was very likely not specifically breed to fight, and probably her parents or even her parents' parents weren't either-it's still in there genetically. Just like a herding or retrieving breed. And because of that you're going to have to accept a few things about Mocha (which in time, you'll realize you should accept about any kind of dog)-she and Arrow may get to a point where they don't get along and will have to be permanently separated. She may get to a point where her and Arrow are okay, but she's not okay with other dogs. And there's also a possibility that'll she'll like all other dogs (though, this one is the least likely). If Mocha is the type of dog that doesn't like other dogs-please don't feel like a bad owner, or like she's a bad girl. It's perfectly normal. All you need from Mocha is for her to like people. If she doesn't-then you've either got some work to do or a big decision to make.
What is your set up for the dogs when you guys can't supervise them? If you're not already-you really should be separating them. Could you imagine-Mocha full grown-her and Arrow getting into it when no one is there to stop it? It could be deadly. Your best bet is to set them up for success. Here's a resource on crate and rotate: http://www.pbrc.net/rotate.html
Are you a fan of the dog park? If so, perhaps this will change your mind. This forum strongly suggests (the majority any way) against dog parks:viewtopic.php?f=2&t=50274
Also, this may be something you're interested-it talks about bringing a new dog into your home. Personally, at 9 months I would consider a modified version of this (I say that, because at the top it is advised against using it for puppies...while Mocha is still kind of a puppy-she's also very close to her teenager/adolences stage).
Two week shut downviewtopic.php?f=6&t=81654&hilit=+two+week
There are a ton of resources here, and really I've just barely skimmed it for you. So much for you to learn
There are a couple of other sites I'd like to suggest that have really good information.http://drsophiayin.com/resourceshttp://www.pbrc.net/http://www.badrap.org/
This forum advocates strongly for responsible ownership of this breed. Don't be afraid to poke around a read the stickies and ask questions-even if they've already been asked...someone will answer or point you in the right direction. The three websites above-Dr Sophia Yin, Pit Bull Rescue Central and Bad Rap also have an almost infinite number of resources for you-tons and tons of good stuff on all of them. Good luck on your search
Be sure to share photos often-we love it!