You can get rid of the red or brass tones from dark brown hair with a product you can get at your local super center or drugstore. You will have to color your hair with a color that cancels out the red however. This can be done with Natural Instincts by Clairol and they sell what is called the Brass Free Collection.
If you dye your hair regularly, and your hair tends to go brassy or orange, do try using the more green based ashy shades and avoid the colors that say "golden" and the like in the name. If you just have a lot of red and brass tones naturally in your hair, Wlrddiva might have the right idea: http://www.clairol.com/naturalinstincts/BrassFree/ni_faqs.pdf. That line of products is supposed to be especially to tone down brass colors in the hair. I haven't used it before, but have had very consistent results with other Natural Instinct products.
If your hair is brassy because of the hardness of the water you wash it in, you should try a clarifying shampoo, and your stylist can probably give you better advice than we can, since they are more familiar with your hair.