When I had my implantation bleeding it was bright red bleeding. I though I was going to mc. I don't think that implantation bleeding is usually brownish colour, because that's an indication of older blood. But, on the other hand, if you are pregnant, brownish blood is a good sign, bright red isn't. I would ask your doc.
I'm sorry I guess I didn't really give you any helpful info.
Keep us posted!
Rose