Will a throw fade in direct sunlight?
If you want to insure your throw won't fade, always check the throw to see if it has UV protection, which very few have and those that do have UV protection are normally designed for outside use. The rest of the throws are like any type of product made from fabric. Over time when they're frequently exposed to the sun, they will fade. The UV rays of the sun break the chemical bonds in the dye and causes it to lose pigmentation. Just as your hair tends to turn blonder in the sun – hence, sun streaked hair – so does fabric fade.
Material and colour types
Certain material and colour combinations are affected by the rays of the sun more than others. Red, for instance, and yellow or any colour between the two are often subject to the most damage. That's because colour comes from the pigmentation reflecting a certain spectrum of colour and absorbing others. The blue spectrum are shorter wavelengths, which have a higher level of energy. Those can be the most damaging and lead to the most colour fading and degradation. You'll notice it more when it comes to red, since yellow simply pales a bit, making it difficult to detect.
If you have a throw made of natural fibres, you'll probably notice more fading than you would from a synthetic material. Cotton tends to fade faster than say, polyester, primarily because polyester holds dye far better. Acetate is a totally different matter. Acetate definitely fades easier. You can find treated acetate, which resists the effects of the sun.
Avoiding sun damage
If you want to avoid damage from the sun, there are several ways to do it. You can keep the throw away from direct sunlight by either keeping the curtains closed or moving it to a darker area of the room. That isn't always the best way, since bright sunlight can be a fabulous accent for a room and a cheery way to start a day.
Using UV film on the window can protect all types of cloth décor in the room, and wooden floors and furniture. There are also UV fabric sprays that can add the protection to a throws. Most people find that frequently shaking out the throw and refolding with a different side up or inverted, if it's open and in direct sunlight can help expand the life expectancy of the throw.