People who are partially-sighted may not be able to see text very well. This may be due to the text being very small or there being little difference (or contrast) between the colour of the text and the colour of the background. Whilst most browsers allow the user to adjust the contrast and size of text, not everyone knows how to do this, so it is helpful to make the text easy to read without adjustment. The formulae necessary to calculate colour contrast are difficult to apply manually but there are many tools available that will automatically determine colour contrast.
Use a colour contrast tool to check whether the size and contrast of text is sufficient.
No example is available.