diff --git a/background.js b/background.js
index 2c2f13e..b15a064 100644
--- a/background.js
+++ b/background.js
@@ -3,6 +3,10 @@ const browserTypeChrome = 2;
 
 const storageTabCountKey = 'tab-count';
 
+const badgeBackgroundColorGrey = '#636c72';
+const badgeBackgroundColorYellow = '#f0ad4e';
+const badgeBackgroundColorRed = '#d9534f';
+
 const getBrowser = () => {
     try {
         return [browser, browserTypeFirefox];
@@ -40,12 +44,25 @@ browser.storage.onChanged.addListener(changes => {
 
 const onTabCountChange = newTabCount => {
     getTabCountFromStorage().then(tabCount => {
+        browser.browserAction.setBadgeBackgroundColor({
+            color: getBadgeBackgroundColor(tabCount),
+        });
         browser.browserAction.setBadgeText({text: tabCount.toString()});
     });
 };
 
+const getBadgeBackgroundColor = tabCount => {
+    if (tabCount < maxNumTabs) {
+        return badgeBackgroundColorGrey;
+    } else if (tabCount === maxNumTabs) {
+        return badgeBackgroundColorYellow;
+    } else {
+        return badgeBackgroundColorRed;
+    }
+}
+
 const setTabCountIntoStorage = tabCount => {
-    browser.storage.local.set({[storageTabCountKey]: tabs.length});
+    browser.storage.local.set({[storageTabCountKey]: tabCount});
 };
 
 const getTabCountFromStorage = () => {