ext on screen is more sensitive than images. An image is generally quite accommodating, it can be quite fuzzy but still recognisable. Text performs a more personal function, people want to be able to read it and to feel comfortable when reading it.

eadability is different from legibility, something might be legible but not that easy to read. This can be especially so in colour and there are plenty of myths around about what colour should or should not be used over which. Often when people are talking about colour in this context they refer to hues, words like red, or green.

In fact hue is not particularly significant as regards readability, relative brightness is the crucial thing. If the difference between the brightness of a piece of text and its background is small, in other words if both are of a similar brightness, then it is likely to be more difficult to read than one where the contrast between brightnesses is greater.

Both those panels are the same hues, they are both magenta, (280° on the colour circle), on orange, (35° on the colour circle) – but at different levels of saturation and brightness. You can do this with red and green too, they’re said by some people to be unreadable one over the other, and so they are if the brightness levels are close, but not if the brightnesss levels are more distant, and note this applies as much to people with colour vision deficiencies as it does to anyone else.

One can start to get into hot water here, saying things like red is readable over green or that hue is of little significance for readability fo people with colour vision deficiencies. Best to try the experiments . . .

My page Text Readability in Colour allows all manner of experiment with coloured text over a different-coloured background, and shows an accurate-enough prediction of readabiliy by barchart.

Note too that where the brightness difference between text and background is small, larger text will be easier to distinquish than text that is smaller.