Hi Brad,
Probably, but not in the upcoming update this week, where we focused on keyboard navigation and other minor improvements. If you have a website for the EU or UK market, you have probably already enabled the default Joomla accessibility module or installed an additional accessibility module (toolkit/widget), which has a dark/yellow colour switcher. If not, you should do so. Of course, it won't solve all accessibility issues, but it's better than nothing.
Indeed, using new SPPB 5.7 you can also make basic color switcher, presented on the right side of website, but it has only colors, not all typical accessibility options (Big Cursor, Read Mode, Text Magnifier, adjust the font size, line height and letter spacing to improve readability etc.). In general, it's a topic for whole book.