Acetylation reaction In the Friedel - Crafts acetylation of bromobenzene, how is it possible to obtain a black-coloured product?

When the acetic anhydride was slowly added to the reactants - $\ce{AlCl3}$, DCM, bromobenzene - a small, hard, yellow lump formed. 

Would this be $\ce{AlCl3}$?

When the acetic anhydride was added, the reflux was initiated. The lump appeared to disappear, leaving behind a dark red solution.

However, when the reflux was turned off, the solution appeared black. I'm trying to think of potential products, such as ortho and para bromobenzene or acetic acid or $\ce{Al(OH)3}$ but why so black?

Does anyone have any ideas?
I assume "DCM" represents dichloromethane, if so...

There is an old paper that describes the formation of a low molecular weight polymer from the double Friedel-Crafts alkylation of benzene by dichloromethane. That's probably what's happening in your reaction as a minor pathway.  The dissolved polymer and tar is what's producing your black solution.

I actually ran that reaction once, I wanted to prepare that polymer.  It didn't work for me, but at the end, after the aluminum chloride had been removed, I did have a dark solution.