Use colour to distinguish between lines on a line chart.
If the data has an implied order, for example, age ranges, use different shades of one colour, or colours with different luminance values, but the same hue and saturation.
Example of chart using different shades of one colour to show an implied order
No implied order
If the data has no implied order, for example, male and female, different colours (hues) can be used.
Example of chart using different colours
Using colour and texture
Lines have a smaller area than bars, which means fewer colours can be distinguished. Try to avoid using more than four shades of one colour on a line chart without using another mechanism to differentiate between them. Using colour and texture can be particularly powerful.