Decide upon a design theme. The way you decorate a room that holds a dusty blue couch will totally depend upon the design of the space. For instance, you will fill the room with a different set of furnishings if you want a country style than you will if you want a cottage style or a traditional living room. Once you've decided what you want the final style of the room to be, you're ready to choose colors.
Find complementary tones and incorporate them into your design. That color wheel that you might have learned about in elementary school art class will come in handy when it's time to find coordinating colors for your room. The color orange is directly across from blue on the color wheel, meaning that shades of orange will work in a complementary way with your blue sofa. Introducing orange shades will work best if you're going for a very country or a very modern space. Peach, a variation of orange, will give your room a country feel, while bright, bold shades of orange will give it a modern edge. Rather than covering your walls in orange, use it as an accent in furnishings like scatter pillows, throws, lamp shades and artwork. Orange is a very warm color that absorbs light and can easily make a room look small, so use it sparingly.
Opt for analogous shades. Another way to choose colors that work with dusty blue is to look at the shade directly adjacent to blue on the color wheel. You'll find that these colors are green and violet. The trick with working either of these colors into the palette of your room is to match shades. Dusty blue is a light hue of blue, so if you want to couple it with green, you'll need an equally light hue of that color. A traditionally styled living room might include beige drapes with small blue and green stripes, artwork that includes blue, green and violet, or an area rug that manages to work two or more of the colors into its pattern. Each of these colors are "cool," meaning that they fill a room with a sense of calm and help it appear more spacious.
Go monochromatic if you want a sophisticated space. If you really want to update the look of that dusty blue couch, play it up by designing a monochromatic color scheme. A monochromatic palette is one that uses variations of the same color to fill the space. For instance, the walls may be a robin's-egg blue, the ceiling a soft bluish-white, and the pillows, throws, lamp shades and area rug may all be navy blue. The adage "less is more" especially applies to a monochromatic room. Because the color is the star of the space, you can omit other trappings like knickknacks and pictures that will just make the space look cluttered.
Make it crisp by introducing white. French country, cottage, beach house and modern country will all pair that dusty blue couch with shades of white. Creamy-white walls, snow-white accents and off-white painted furniture will help minimize the intensity of the blue sofa while introducing a style of their own.
Edit your furniture. Blue is an easy color to overdo, so if possible, make it the couch the only solid blue piece of furniture in the room. Unless you go with a monochromatic color scheme, one blue sofa makes enough of a design statement to carry a room.