Whether flat, silk, low-sheen, semi-gloss or glossy, sheens can dramatically change how a colour looks, especially with glossy finishes. Gloss can add depth to colour, and is also very reflective, which not only changes perception of the colour but will also reveal surface imperfections. The glossier the finish, the more light bounces off the walls. Flat finishes on the other hand reflect the least amount of light, and conceal more, making them the best choice for imperfect walls.