If you're using components, it's the same as Tailwind, just put your CSS module files next to the component, or use compile time CSS in TS frameworks like PandaCSS to have them in the code itself. For shared conventions that is the purview of the design system and you'd have CSS tokens for various colors etc. Anything you can do in Tailwind you can of course do in CSS modules because it's CSS at the end of the day.