Brass can be spray painted any color as long as the surface is properly prepared. A coarse-grit sandpaper can scuff up the brass a bit so the paint has something to adhere to. Otherwise, the new paint layer is prone to peeling.
Sandpaper marks should not be so deep that they appear to be scratches under the paint. An acetone-dampened cloth can be used to wipe the area clean after sandpapering. Once the acetone dries, masking tape can be used to mark off any areas not to be painted. If the brass is positioned outside regularly, then it is best to use a corrosion-resistant primer before applying spray paint. For brass that may be heated, a heat-resistant spray paint should be used.