Prior to having ever set foot in a Rug & Home store, I admittedly had never shopped for a rug in my life. Like most wide-eyed individuals, I was overwhelmed by the sizes and variety of options these works of art come in. You can only imagine my surprise when I settled on liking a slate grey number, it's dropped to the floor, and immediately the color has changed. Huh? To a rug shopping newbie, the concept of light and dark side can be a "wow" moment. What may appear bright and "light" on one side, changes to darker and less lustrous on the other. This is true of all wool rugs and even some machine made rugs though the intensity will vary based on color palette and fibers.
Silk rugs have the most variation in sheen. This variation is the nature of the nap of the rug (compare it to vacuuming carpet and the 'lines' that appear when vacuuming) and not a defect of any sort. If you're looking for an exact coloration throughout, your best bet may be a tufted or machine made rug, however, I would argue that the reversibility of sorts may be beneficial for certain seasons when you may want a different perspective on color. Silver sheen may be bright in a dull winter, but a grey tone may be more suitable to a colorful summer. Does lighting really make a difference? Absolutely! Look at both sides of your rug when shopping to get the full experience of color.