Should be fine. If it isn't too light, you've said dark brown so my assumption is it'll match a dark grey suit without an issue.
You could put them on and put up a photo for people to assess.
Doesn't matter. A briefcase is basically luggage. As long as it doesn't look like total crap, it's fine.
This. As he said, it is a piece of luggage, not a piece of clothing that necessarily needs to be matched. A brown leather bag can tie the whole thing together with some extra class.
First. World. Problem.
Next up, polishing your shoe soles....
There you go again...
First issue.... look between your legs.... is there something hanging there? Yes? Then why are you trying to match your shoes and purse? If its not a purse, then it doesnt matter if its neon blue.... its just a bag to carry shit in. As far as it mattering these days.... it never mattered all that much to men.
^ This. I was going to say that, too (though not as creatively). Men don't need to match briefcases and shoes/belts any more than women do with their briefcases. Whatever carries your stuff adequately without killing your arms or back and doesn't look beat up, you're good.
However, given the option, sticking to something in the same color family is still considered preferable.
I'm sure your penis shrunk just from reading his question.
Lots of people taking this way too seriously.