Word to know
Contrast
How different text is from the colour behind it.
Also called: text too light, hard to read, faded writing, not enough difference between text and background
The difference in lightness between words and their background. When the two are too close, such as pale grey on white, the words become hard to read.
Using it in a prompt
Keep body text at a contrast ratio of at least 4.5 to 1. No pale grey text on a white background.
Pale grey text on white is the most common readability failure, and it is usually chosen because it looks calm on a large bright screen in a well lit room. It stops working on a phone outdoors.
The ratio is measurable, so name the number rather than asking for readable text. 4.5 to 1 is the standard for body text.