How would you choose colour if you want to produce the most readable text?

Colours can contrast in hue, value and saturation. Hue and saturation are not important for legibility, but value does. Black and white create the highest contrast possible. That’s because white has a 100% brightness value, whereas black has a brightness value of 0%. It is common to use a combination of them to avoid a dull page.
Reason:
Text readability depends on the ease of distinguishing letter and word shapes which in turn depends on the discrimination of fine detail. High achromatic contrast maximizes this aspect of perception. Since the chromatic system has 1/5 the spatial resolution of the achromatic system, color cannot produce fine detail.

Contrast of value:
Common example:
Black text on white paper/white text on black paper.
Color of print and background:
1. Black print on white background is more legible than white print on blackground, due to the smaller number of fixation pauses. Three fourths of readers prefer black type on a white background.
2. The legibility of black print on tinted paper varies, according to the reflectance of the tinted paper. If the reflectance is over 70%, there is no notceable loss in legibility for type over 10 points in size.
3. The great the brightness contrast between print and background, the higher the legibility.
4. Dark ink on a light shade of colour ink or coloured paper results in the most legible combinitions of colored ink on a colored background.

Contrast of value and hue combination:
The further way on the colour wheel of two colors are, the higher hue contrast.
The larger differences in lightness of two colors are, the higher value contrast.
Example:
A bright warm color and a dark cold color. (cold colours appear to be more distant, while warm colour appear to be closer)
Such as: bright red for text and dark blue for background

Contrast of value and saturation combination:
The further distance of two colours in saturation, the higher saturation contrast.
And The larger differences in lightness of two colors are, the higher value contrast.
Example:
A interesting effect of saturation contrast is that a setting of colour with different saturations set against a grey background.
Such as:
Rich red for text on light grey background.

Colour contrast does not achieve legibility:
Contrast only hue or saturation
Examples:
red-blue, green-yellow, green-white, green-gray ("button gray", the Windows standard gray) etc. (high hue contrast, they have small value contrast)

Summarize:
The best combinations have the two brightest colors, white and yellow, contrasted with the two darkest colors, black and blue: black-white, blue-white, blue-yellow, and black-yellow. Red has a dark intermediate brightness and works reasonably well against all backgrounds but blue.