add a demonstration of custom components

Change-Id: Ide51413f1cf66b8275f130f1478fa02b55923a2f
diff --git a/client/src/themes/default.js b/client/src/themes/default.js
index 6764097..db10bde 100644
--- a/client/src/themes/default.js
+++ b/client/src/themes/default.js
@@ -16,6 +16,9 @@
   },
   typography: {
     fontFamily: "Ubuntu",
+    allVariants: {
+      color: "black"
+    },
     h1: {
       fontWeight: 400,
       fontSize: "26px",