Fun #retrocomputing fact of the day: The #Apple II, one of the first home #computers to have color video support, did not output color video. Show more
NTSC color displays synchronize to a ~3.58 MHz signal, the color burst signal, to extract color information imposed at that frequency.
Apple II video outputs a monochrome signal at 2 or 4 times that frequency, and then when a graphics mode is enabled, the color burst signal is also enabled. The display is effectively tricked into displaying color.
Also one thing I left out - this trades resolution for color.
The native output of an Apple II in hi-res mode is 280 pixels wide, and double-hi-res is 560 pixels wide. With the color burst enabled, that becomes effectively 140 pixels.
Some monitors at the time had switches to disable color, if you wanted monochrome graphics - especially important later in the 8-bit Apple II's life, as GUIs started appearing. Unwanted artifact color made text unreadable.
A review that I found of A2Heaven's Apple //c VGA adapter (which has to emulate all of this for color to work at all) illustrates this quite nicely: http://www.oldtechnewtech.com/apple-iic-vga-review/
Without color enabled, the screen is crisp and perfectly readable: http://www.oldtechnewtech.com/wp-content/uploads/2016/01/edited_20160110_164253.jpg
With it enabled, it's a complete and total mess: http://www.oldtechnewtech.com/wp-content/uploads/2016/01/edited_20160110_164311.jpg