I have made it 2 times, and both ended up kind of pink. I think it would take a whole lot of blackerries to end up with red or black. Maybe some sort of coloring would help.
I just made a blackberry mead using frozen store bought balckberries and it is very, very dark. I used 8 lbs of blackberries in 5 gallons, for what that is worth.
Sounds like too little fruit, or the results of steam juicing.
Frank, use at least 4 pounds of fruit per gallon, and ferment on the fruit and it will be as dark as any good red wine. It also helps to use a yeast good for fixing color.