use https://github.com/nunocoracao/blowfish.git

themes/blowfish/assets/js/mermaid.js

@@ -0,0 +1,20 @@
+function css(name) {
+  return "rgb(" + getComputedStyle(document.documentElement).getPropertyValue(name) + ")";
+}
+
+mermaid.initialize({
+  theme: "base",
+  themeVariables: {
+    background: css("--color-neutral"),
+    primaryColor: css("--color-primary-200"),
+    secondaryColor: css("--color-secondary-200"),
+    tertiaryColor: css("--color-neutral-100"),
+    primaryBorderColor: css("--color-primary-400"),
+    secondaryBorderColor: css("--color-secondary-400"),
+    tertiaryBorderColor: css("--color-neutral-400"),
+    lineColor: css("--color-neutral-600"),
+    fontFamily:
+      "ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,segoe ui,Roboto,helvetica neue,Arial,noto sans,sans-serif",
+    fontSize: "16px",
+  },
+});