While the scenarios and techniques here help avoid some serious issues and confusion, they are not exhaustive. There are many complex contexts and use cases when it comes to accessibility, such as users with low vision who need a high color contrast ratio to see UI. There are some great tools and resources to learn from and work on these issues out there. Here are a few reads we recommend.
We'll continue to work on these under the larger topic of accessibility, but in the meantime, let us know if any bugs or issues.