For #8114: Restore normal UI when a library fragment is detached.

app/src/main/java/org/mozilla/fenix/library/LibraryPageFragment.kt

@@ -4,11 +4,15 @@
 
 package org.mozilla.fenix.library
 
+import androidx.appcompat.widget.Toolbar
 import androidx.fragment.app.Fragment
+import mozilla.components.support.ktx.android.content.getColorFromAttr
 import org.mozilla.fenix.HomeActivity
+import org.mozilla.fenix.R
 import org.mozilla.fenix.browser.browsingmode.BrowsingMode
 import org.mozilla.fenix.ext.components
 import org.mozilla.fenix.ext.hideToolbar
+import org.mozilla.fenix.ext.setToolbarColors
 
 abstract class LibraryPageFragment<T> : Fragment() {
 
@@ -27,4 +31,14 @@ abstract class LibraryPageFragment<T> : Fragment() {
         (activity as HomeActivity).browsingModeManager.mode = BrowsingMode.fromBoolean(private)
         hideToolbar()
     }
+
+    override fun onDetach() {
+        super.onDetach()
+        context?.let {
+            activity?.findViewById<Toolbar>(R.id.navigationToolbar)?.setToolbarColors(
+                it.getColorFromAttr(R.attr.primaryText),
+                it.getColorFromAttr(R.attr.foundation)
+            )
+        }
+    }
 }