Colours and Links
The colours for text and backgrounds should always be high contrast eg. black and white. This makes the text more legible, reduces eye strain and – importantly – makes it easier for people with colour blindness and other visual impairments to use the site.
Links in the main body of the text should always be the same colour and should be underlined or have their background colour set differently to distinguish them from regular text. You can have a dotted line, dashed line or solid line under your links. The solid line is recommended as it’s most commonly associated with links, but if you want to freshen up a design consider using one of these alternatives.
A different colour should be used for visited links so that users can see whereabouts they have already visited on the site. A paler or darker version of the unvisited link is the most common way of signifying a visited link. Some people remove the underline but that’s not a good idea for reasons explained below.
Possibly the most important rule to follow when using colour is the following: don’t use colour alone to signify meaning. For example, don’t remove the underline from links. If you do this, colourblind individuals may have no way of telling where the links are. Similarly, if you are using colours to signify the importance of or difference between certain elements, try to do this in another way as well.
It’s estimated that 9% of the UK population has some form of colourblindness. Don’t alienate a large chunk of your audience by using colours that prevent them from getting the most out of your site.