Welcome! I think black and brown would both look good! As some have mentioned, there are some rules about when to wear what. But like all fashion rules, some adhere to all of them all the time, some never do, and most find a happy medium between the two extremes.

Which would you prefer to wear? Buy that first. Don't worry, whichever color leather you purchase, you'll be wanting the other color as well, soon enough.

Also, since I am putting this next sentence in brackets, it doesn't exist, ergo it's not off-topic. [Congrats TheScot!]