Screen accessibility resides in a joint effort from developers and you, designers. Many different aspects of designing an inclusive experience play an important role when combined together.
Colors
What may seem completely standard to some of us, may not to others. Color is one of those aspects we don't really think much about. Most designers probably don't have any color disability, and thus cannot really understand the need of a contrast thresold.
Making a good-looking color palette is easy. Making an accessible color palette is not much harder. Color contrast is important in many ways: not everyone is able to see colors correctly, or any color at all. It is really important we don't base visual feedback on only sensory information.
Writing
From microcopy to kerning, it is crucial not to oversee those characteristics. You would be pretty disapointed to have crafted an experience that is unreadable to some people.
Typography doesn't only rely on choosing the latest trendy font. Text legibility is an important factor which depends on your font size, font characteristics, kerning, leading, and your color palette as well. See? Everything connects.
Focus
This can help anyone figure out your interface easier. There is no secret recipe for good design, but a good understanding of the Gestalt fundamentals can greatly help.
Four different perception "laws" will help you craft better structured interfaces, which will be effortless to navigate with the eyes, or a keyboard as well. This practice follows what our brain originally does: creating structured sets.
Motion
Motion is a module that completes Focus. It adds a level of visual confort that ease the screen experience and which can reduce eye distraction, because of a focal focus.
Although, there is a motion thresold designers should not cross, in order to prevent motion sickness and avoid triggering visual sensitivities.