So it is very important to have a well selected palette, or the color will spread easily among consecutive pixels in the scan line of the image.
[2] The Enhanced Graphics Adapter (EGA) supports all CGA modes and add three more: two 320×200 and 640×200 graphic modes, both with the full CGA 16-color palette (intended to be used with the same "digital RGB" CGA color monitor of 200 scan lines) and an extra 640×350 graphic mode with 16 colors chosen from a 6-bit RGB (64 colors) palette for what IBM then called an "analog RGB"[citation needed] type monitor.
Thus, the EGA signal from the computer to this kind of monitor had two wires for each primary red, green and blue.
IBM developed a true analog video interface later, for the more advanced MCGA and VGA display adapters and monitors (and earlier, for the Professional Graphics Controller, announced simultaneously with the EGA) which are unrelated to (and incompatible with) the EGA "analog" monitors; see the next section.
The colors are then mapped internally to the correspondent luminance gray, (the sum of the 30% of the red signal, the 59% of the green and the 11% of the blue) giving a 16-shades from a 64-grayscale palette.
Targeted at the CAD market this mode has limited software support, although some clone boards exist.
Some of the first portable PCs featured a flat monochrome plasma display with a VGA in shades of red.
Also, some SVGA cards support 15- and 16-bit RGB Highcolor modes, with 32,768 or 65,536 simultaneous colors on screen in 640×480 and higher resolutions.
In the 1990s, most manufacturers adhered to the VESA BIOS Extensions (VBE), used for enabling standard support for advanced video modes (at high resolutions and color depths).