It is an error not to specify a background color when

It is an error not to specify a background color when specifying text color because the default background color set by users is unknown and cannot be tested for sufficient contrast. Note 3: For the purposes of approval criteria 1.4.3 and 1.4.6, contrast is measured against the specific background against which the text is displayed under normal operating conditions. In addition, it is more difficult to change the contrast and color combinations of the foreground and background images of the text, which is necessary for some users. Therefore, in this recommendation, contrast is calculated so that color is not the determining factor, so that people with color vision problems can achieve the correct contrast between text and background. Text in 18 paragraphs or bold text in 14 paragraphs is considered large enough to require a lower contrast ratio. Note: Some people with cognitive disabilities require low contrast color schemes or shades. Therefore, we allow and encourage authors to provide mechanisms for adjusting foreground and background content colors. Note 4: The background color is the preset content color on which text should be displayed in normal use. The 3:1 contrast ratio is the minimum recommended by [ISO-9241-3] and [ANSI-HFES-100-1988] for standard text and images. When authors create images containing large amounts of text, they should make sure that the resulting image text is approximately 1.2 and 1.5 inches or 120% and 150% of the size of standard text displayed by the browser.