HDMI 1.3 Specificaion for Deep Color

Deep Color™ lets HDTVs and other displays go from millions of colors to billions of colors allowing consumers to enjoy unprecedented vividness and accuracy of color on their displays. Deep Color™ eliminates on-screen color banding, for smooth tonal transitions and subtle gradations between colors. It enables increased contrast ratio, and can represent many times more shades of gray between black and white.

HDMI 1.3 supports 30-bit, 36-bit and 48-bit (RGB or YCbCr) color depths, up from
the 24-bit depths in previous versions of the HDMI specification.

• Lets HDTVs and other displays go from millions of colors to billions of colors
• Eliminates on-screen color banding, for smooth tonal transitions and subtle gradations between colors.
• Enables increased contrast ratio
• Can represent many times more shades of gray between black and white. At 30-bit pixel depth, four times more shades of gray would be the minimum, and the
  typical improvement would be eight times or more.
  

Good Source for Deep color: www.hdmi.org