8.8 WCAG 2.1 Success Criterion 1.4.1 − Use of Colour
Do not rely solely on colours to convey information. It is impossible to be sure that everybody perceives colours in the same way (for example the visually impaired or those who are colour blind), and what may seem obvious to one person may be missed by another.
Before Rectification
In the example above, the three lines are of different colours, however, a colour blind or visually impaired person may not be able to detect this colour difference.
After Rectification
By making the items have different shapes, someone who cannot perceive colours can differentiate between these items through the different shapes in the graph.
WCAG 2.1 Reference:
https://www.w3.org/WAI/WCAG21/Understanding/use-of-color
