My phone is in dark mode so amethyst is in dark mode.

Try dark theme in Android system

Yeah it defaults to your system theme. FYI, having your phone in dark mode all the time saves battery, because you're not illuminating thousands of pixels for no reason, just illuminating the text.

Don't worry, you still can get the zaps

If you are using android developers setting ms will do the magic. Just select force darkmode under developers setting. Every app will appear in dark mode. Hope this helps