16-bit RGB
Most modern systems support 16-bit color. It is sometimes referred to as Highcolor (along with the 15-bit RGB), medium color or thousands of colors. It utilizes a color palette of 32×64×32 = 65,536 colors. Usually, there are 5 bits allocated for the red and blue color components (32 levels each) and 6 bits for the green component (64 levels), due to the greater sensitivity of the normal human eye to this color. This doubles the 15-bit RGB palette.
The 16-bit RGB palette using 6 bits for the green component:
The Extended Graphics Array (XGA) for IBM PS/2 also uses the 16-bit RGB palette.
It must be noticed that not all systems using 16-bit color depth employ the 16-bit, 32-64-32 level RGB palette. Platforms like Sharp X68000 or the Neo Geo videogame console employs the 15-bit RGB palette (5 bits are used for red, green, and blue), but the last bit specifies a less significant intensity or luminance. The 16-bit mode of the Truevision TARGA/AT-Vista/NU-Vista graphic cards and its associated TGA file format also uses 15-bit RGB, but it devotes its remaining bit as a simple alpha channel for video overlay.
Read more about this topic: List Of Monochrome And RGB Palettes, Non-regular RGB Palettes