MyComponents.tsx

// colors.ts
export const colors = {
  primary: "#0d6efd",
  border: "#ddd",
  /* ... */
};
// MyComponent.tsx
function MyComponent({ fontSize }) {
  return (
    <p
      css={{
        color: colors.primary,
        fontSize,
        border: `1px solid ${colors.border}`,
      }}
    >
      ...
    </p>
  );
}