I'm just here to help show how the modal floats over other content, and how the dropshadow partially obscures content only in a normal display mode, and not Forced Colors mode. Forced Colors mode is really interesting, and I'm glad it exists because it helps people use computers, and also it's an open standard now, so everyone can enjoy and contribute to it.
Designing for Forced Colors mode isn't too difficult once you know that it exists. It's mostly about making a good habit to check it in the first place, and then making small, surgical tweaks rather than complete overhauls.
Still here? Cool. Don't forget to test your websites and web apps with the Tab key and make sure that each interactive element has a visible focus state. That'll help a whole lot to make things accessible!