Jarvo when I visit your website, the primary tags show white text on pink background, so it seems to work as intended?
Is the forum using any kind of night/dark mode extension or custom code, are you using any dark mode plugin in your browser and is your operating system in dark mode?
I tried in Firefox using no special browser plugin. I tried changing the browser/operating system dark mode preference but your website appears to look the same no matter if it's set to auto/light/dark. This is the expected behavior on a basic Flarum installation without extensions.
The color of the text will change according to the tag background, so maybe you tweaked the color in the meantime or added some additional CSS?