Walk around the living-room and note the colors of your color scheme. You should have at least one to a maximum of three dominant colors.
Determine if you want your couch to match your one dominant color or one of your two or three colors of your color scheme or contrast your color scheme. For example, an all white couch in an all-white room can be quite striking, as can an orange couch in an all-white room.
Consider a neutral-colored couch. Sometimes you can have a couch that doesn't match any shades of your color scheme, if it is a harmonious neutral color. For example, a light gray couch can go well with a red and yellow room as it can a purple- and green-styled room. Choosing a neutral color prevents the room from looking overly matchy-matchy.
Pick a patterned couch that either incorporates two or three of the colors of your color scheme, or none of the colors of your color scheme, such as a blue floral print couch in an all-white room. However, if you choose a patterned couch, it should be the only patterned item in the room.