There are a number of ways to add a label in Gmail. Select one or more emails and you will see the Labels button appear at the top of Gmail; go to Mail Settings and choose the Labels tab; or start a search, create a Filter and add a new label. However you choose to create a label, it will appear in your left hand menu so you can easily filter the labelled emails.
At this point you can colour code your label, and the effect is dramatic. By choosing to colour your labels you can bring your inbox to life – using colour to pick out emails from important clients, or your boss. To add a colour to your label, click on the down arrow next to its name in the left hand menu. You can add a standard colour or customise your own.