Generally for body text, a black-to-white ratio of 60-80% is preferred for best readability. On a white background, in practice this means setting text to a hex color between #333333 and #666666, which is equivalent to rgb(51, 51, 51) and rgb(102, 102, 102). In CSS, a background-color property of grey or gray is equal to #808080 or rgb(128, 128, 128), which is a darkish grey. It is dark enough to suggest using white as the text color for best contrast.