Because red is a color that demands attention, a couch in that color is sure to stand out in a room. It is best to play up that feature in the design by making the couch the focal point and letting the rest of the decor complement it.
One way to create a nice decor is to use neutrals in the rest of the room. Pillows in neutral tones can be placed on the couch so that it fits in with the rest of the decor. Browns and tans throughout the space can create a soft and understated contrast to the bright tones of the couch. Another option is to use black and white throughout the rest of the space.
For a bold look, add vibrant colors. Use red elsewhere in the room. This helps take attention off the couch and instead puts the focus on the overall space. Bold artwork on the walls can add a complementary touch. All the walls of the room can be painted red, or the red could be focused on a single accent wall; just make sure the red paint is complementary to the red tone of the couch. Yellow or gold are good colors to pair with red to give a rich look to a room.