Creek writes that for websites that are considered easy to read, "they all have one thing in common - excellent contrast." This can mean black text on white background, which is most common in printed material, or any combination of colors that contrast well. On the contrary, yellow on white or other pairings of similar shades have the least amount of contrast and are difficult to view as a result.
Creek writes that colored text is nearly always a problem for anyone to read. While he cautions against using colored text, Creek indicates that it would work if the colors are carefully chosen to ensure there is enough contrast with the background color. Darker colors work best, such as black, burgundy or dark blue on light or white background.
Richard Hall, professor of Information Science and Technology at Missouri University of Science and Technology, adds that studies generally show that black text on white is most readable and that color combinations that included black were more readable than those that did not. Darker text on light backgrounds consistently rated higher in readability studies.
As noted in the Web Developer's Virtual Library, between 6 and 8 percent of all people are colorblind and would have great difficulty viewing colors as compared to those who see colors well. Lee Creek, writing for the Library, explains that colorblind readers find it particularly challenging when red and green are used together. Conversely, black and white is the worst color combination for those who are dyslexic. High contrast makes text unreadable for them, so it's often preferable for them to change the shading a bit so the contrast isn't so extreme.
The best way to ensure optimum readability of text is to allow a user to select his own background color, according to Creek. Developers can also code the web page so that users can select their favorite font, text color and other elements to make it easy for them to read the copy on the page. Some web browsers allow users to choose their background and font colors regardless of how a page is coded.