Unique colors are non-variants of each other; dark blue, teal blue and navy have the same base (blue), this will cause problems later as we will identify one part of the case to be modified with one color (to become transparent for example). If you use similar colors, it can cause parts of the picture we want to keep intact to change. Red, blue, green yellow and so on are unique.
Notice each section of the case has a different color. There are two colors that could clash in our photo; the shadow and the background (white background, off-white shadow). We want to keep the shadow off white so we’ll change the background to blue.
