First, decide if you want to use lighter colors to contrast with the brown, or all dark colors. For light colors, you can choose white or cream paint for the walls, towels, rugs and other accessories. Depending on the particular color of your granite, you can also use light pink, peach or tan as a second color. Light, warm colors such as pink or peach are flattering to skin tones. Tan might harmonize as a lighter shade of the brown granite.
Dark wall colors are very chic now and create an elegant, shadowy effect. You might choose dark brown walls and towels, or a deep terracotta, or even black -- whichever colors harmonize with the particular shade of your granite. If you go dark, you might want metallic accents or glass in your lighting, mirrors and faucets to give some sparkle to the space. Be sure to include adequate lighting.
Brown may swing to either the pinkish or yellowish side of the spectrum. Be careful to choose other colors that harmonize. If the granite is yellowish brown, shades of tan, yellow, beige or even gray-green might look best. If the granite is pinkish brown, try warmer colors such as pink, light gray or possibly light blue or lavender.
Because this is a bathroom, consider whether the colors you choose are flattering to your skin. A yellow and brown bathroom might make you look sallow when you see yourself in the mirror. For most people, warmer colors are more flattering.