When you say it's brown, what sample are you looking at? Because your hydrometer is going to look much lighter than a glass of beer. I brewed an imperial stout a couple weeks ago that was just dark brown in the hydrometer flask. Of course, in the carboy it's black as a tire. Let it completely finish fermenting before making a judgement on the color - yeast reflect light and make it seem lighter.
I generally feel like above 30 SRM is black, though when held up to a light you might get some ruby-brown highlights at the edge of the glass.
Here's a link to the BJCP stout guildelines: http://www.bjcp.org/styles04/Category13.php
You'll notice that some of the styles tolerate some colors that are slightly less than black. Just wait 'til it's fermented, cleared, bottled, carbonated, and sitting in your drinking glass before you start worrying about the little things!