Custom colors/themes with Geist

[averwhy]

Hi, im fairly new to web dev, im trying to figure out how to use my own colors for Geist components. The following doesn't work: <Grid xs={6}><Card shadow width="100%" className="bg-slate-800"/></Grid> (I am using tailwindcss.)

I've found the color guide on the site, however it says goto use-theme to learn more, but i have having trouble making sense of that. I do not use themes I only have one theme (dark) in my project, and that page does not touch on how to add custom colors in any capacity. Thanks in advance