Color banding is a digital graphic artifact that results in a visible stepping of the shades in a gradient. It stems from a problem of inaccurate color presentation, where graduated colors break into larger blocks of a single color, thus reducing the smooth look of a proper gradation. In 24-bit color modes, 8 bits per channel is usually considered sufficient to render images in Rec. 709 or sRGB. However, in some cases, there is a risk of producing abrupt changes between shades of the same color. For instance, displaying natural gradients (like sunsets, dawns, or clear blue skies) can show minor banding.
Colour banding is more noticeable with fewer bits per pixel (BPP) at 16–256 colors (4–8 BPP), where not every shade can be shown without dithering.
Possible solutions include the introduction of dithering and increasing the number of bits per color channel. Blurring does not fix this unless one actually increases the number of levels available so that the blur can render color in intermediate levels.