8.7 WCAG 2.1 Success Criterion 1.3.3 − Sensory Characteristics
Do not rely solely on sound, shape, size or visual location to provide instructions for understanding content. For example, if instructions say "to submit, click the button to the right" , a visually impaired person will not know where that button is.
Before Rectification
In the example above, it is only clear to a person who can see the webpage that he/she needs to click the green arrow. This will not be clear to a visually impaired person.
After Rectification
The correct way to do this is to label the button and ensure clear instructions are in place to tell people which button to use and how to use it.
WCAG 2.1 Reference:
https://www.w3.org/WAI/WCAG21/Understanding/sensory-characteristics