diff --git a/packages/SystemUI/shared/src/com/android/systemui/shared/regionsampling/RegionSampler.kt b/packages/SystemUI/shared/src/com/android/systemui/shared/regionsampling/RegionSampler.kt
index 9a00447615049..0ca2f7a363112 100644
--- a/packages/SystemUI/shared/src/com/android/systemui/shared/regionsampling/RegionSampler.kt
+++ b/packages/SystemUI/shared/src/com/android/systemui/shared/regionsampling/RegionSampler.kt
@@ -263,6 +263,8 @@ constructor(
                 (colors?.colorHints?.and(WallpaperColors.HINT_SUPPORTS_DARK_TEXT)) !=
                     WallpaperColors.HINT_SUPPORTS_DARK_TEXT
             )
+        if (DEBUG)
+            Log.d(TAG, "onColorsChanged() | region darkness = $regionDarkness for region $area")
         updateForegroundColor()
     }
 
diff --git a/packages/SystemUI/src/com/android/keyguard/ClockEventController.kt b/packages/SystemUI/src/com/android/keyguard/ClockEventController.kt
index 8ea4c31a5ac94..84a2c25999a05 100644
--- a/packages/SystemUI/src/com/android/keyguard/ClockEventController.kt
+++ b/packages/SystemUI/src/com/android/keyguard/ClockEventController.kt
@@ -15,18 +15,18 @@
  */
 package com.android.keyguard
 
-import android.app.WallpaperManager
 import android.content.BroadcastReceiver
 import android.content.Context
 import android.content.Intent
 import android.content.IntentFilter
 import android.content.res.Resources
 import android.text.format.DateFormat
-import android.util.TypedValue
 import android.util.Log
+import android.util.TypedValue
 import android.view.View
 import android.view.View.OnAttachStateChangeListener
 import android.view.ViewTreeObserver
+import android.widget.FrameLayout
 import androidx.annotation.VisibleForTesting
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.repeatOnLifecycle
@@ -99,6 +99,28 @@ constructor(
 
                 if (!regionSamplingEnabled) {
                     updateColors()
+                } else {
+                    clock?.let {
+                        smallRegionSampler = createRegionSampler(
+                                it.smallClock.view,
+                                mainExecutor,
+                                bgExecutor,
+                                regionSamplingEnabled,
+                                isLockscreen = true,
+                                ::updateColors
+                        )?.apply { startRegionSampler() }
+
+                        largeRegionSampler = createRegionSampler(
+                                it.largeClock.view,
+                                mainExecutor,
+                                bgExecutor,
+                                regionSamplingEnabled,
+                                isLockscreen = true,
+                                ::updateColors
+                        )?.apply { startRegionSampler() }
+
+                        updateColors()
+                    }
                 }
                 updateFontSizes()
                 updateTimeListeners()
@@ -110,8 +132,25 @@ constructor(
                 }
                 value.smallClock.view.addOnAttachStateChangeListener(
                     object : OnAttachStateChangeListener {
-                        override fun onViewAttachedToWindow(p0: View?) {
+                        var pastVisibility: Int? = null
+                        override fun onViewAttachedToWindow(view: View?) {
                             value.events.onTimeFormatChanged(DateFormat.is24HourFormat(context))
+                            if (view != null) {
+                                val smallClockFrame = view.parent as FrameLayout
+                                pastVisibility = smallClockFrame.visibility
+                                smallClockFrame.viewTreeObserver.addOnGlobalLayoutListener(
+                                        ViewTreeObserver.OnGlobalLayoutListener {
+                                    val currentVisibility = smallClockFrame.visibility
+                                    if (pastVisibility != currentVisibility) {
+                                        pastVisibility = currentVisibility
+                                        // when small clock  visible, recalculate bounds and sample
+                                        if (currentVisibility == View.VISIBLE) {
+                                            smallRegionSampler?.stopRegionSampler()
+                                            smallRegionSampler?.startRegionSampler()
+                                        }
+                                    }
+                                })
+                            }
                         }
 
                         override fun onViewDetachedFromWindow(p0: View?) {
@@ -141,21 +180,19 @@ constructor(
 
 
     private fun updateColors() {
-        val wallpaperManager = WallpaperManager.getInstance(context)
         if (regionSamplingEnabled) {
-            regionSampler?.let { regionSampler ->
-                clock?.let { clock ->
-                    if (regionSampler.sampledView == clock.smallClock.view) {
-                        smallClockIsDark = regionSampler.currentRegionDarkness().isDark
-                        clock.smallClock.events.onRegionDarknessChanged(smallClockIsDark)
-                        return@updateColors
-                    } else if (regionSampler.sampledView == clock.largeClock.view) {
-                        largeClockIsDark = regionSampler.currentRegionDarkness().isDark
-                        clock.largeClock.events.onRegionDarknessChanged(largeClockIsDark)
-                        return@updateColors
-                    }
+            clock?.let { clock ->
+                smallRegionSampler?.let {
+                    smallClockIsDark = it.currentRegionDarkness().isDark
+                    clock.smallClock.events.onRegionDarknessChanged(smallClockIsDark)
+                }
+
+                largeRegionSampler?.let {
+                    largeClockIsDark = it.currentRegionDarkness().isDark
+                    clock.largeClock.events.onRegionDarknessChanged(largeClockIsDark)
                 }
             }
+            return
         }
 
         val isLightTheme = TypedValue()
@@ -168,23 +205,6 @@ constructor(
             largeClock.events.onRegionDarknessChanged(largeClockIsDark)
         }
     }
-
-    private fun updateRegionSampler(sampledRegion: View) {
-        regionSampler?.stopRegionSampler()
-        regionSampler =
-            createRegionSampler(
-                    sampledRegion,
-                    mainExecutor,
-                    bgExecutor,
-                    regionSamplingEnabled,
-                    isLockscreen = true,
-                    ::updateColors
-                )
-                ?.apply { startRegionSampler() }
-
-        updateColors()
-    }
-
     protected open fun createRegionSampler(
         sampledView: View,
         mainExecutor: Executor?,
@@ -202,7 +222,10 @@ constructor(
         ) { updateColors() }
     }
 
-    var regionSampler: RegionSampler? = null
+    var smallRegionSampler: RegionSampler? = null
+        private set
+    var largeRegionSampler: RegionSampler? = null
+        private set
     var smallTimeListener: TimeListener? = null
     var largeTimeListener: TimeListener? = null
     val shouldTimeListenerRun: Boolean
@@ -319,7 +342,8 @@ constructor(
         configurationController.removeCallback(configListener)
         batteryController.removeCallback(batteryCallback)
         keyguardUpdateMonitor.removeCallback(keyguardUpdateMonitorCallback)
-        regionSampler?.stopRegionSampler()
+        smallRegionSampler?.stopRegionSampler()
+        largeRegionSampler?.stopRegionSampler()
         smallTimeListener?.stop()
         largeTimeListener?.stop()
     }
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitchController.java b/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitchController.java
index 8f17edd23f55c..25ad3af52d04f 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitchController.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitchController.java
@@ -531,9 +531,13 @@ public class KeyguardClockSwitchController extends ViewController<KeyguardClockS
         if (clock != null) {
             clock.dump(pw);
         }
-        final RegionSampler regionSampler = mClockEventController.getRegionSampler();
-        if (regionSampler != null) {
-            regionSampler.dump(pw);
+        final RegionSampler smallRegionSampler = mClockEventController.getSmallRegionSampler();
+        if (smallRegionSampler != null) {
+            smallRegionSampler.dump(pw);
+        }
+        final RegionSampler largeRegionSampler = mClockEventController.getLargeRegionSampler();
+        if (largeRegionSampler != null) {
+            largeRegionSampler.dump(pw);
         }
     }
 
diff --git a/packages/SystemUI/tests/src/com/android/keyguard/ClockEventControllerTest.kt b/packages/SystemUI/tests/src/com/android/keyguard/ClockEventControllerTest.kt
index 3f1560bc5fcea..f7471087a0e36 100644
--- a/packages/SystemUI/tests/src/com/android/keyguard/ClockEventControllerTest.kt
+++ b/packages/SystemUI/tests/src/com/android/keyguard/ClockEventControllerTest.kt
@@ -53,6 +53,7 @@ import org.junit.Before
 import org.junit.Rule
 import org.junit.Test
 import org.junit.runner.RunWith
+import org.mockito.ArgumentMatchers.anyBoolean
 import org.mockito.ArgumentMatchers.anyFloat
 import org.mockito.ArgumentMatchers.anyInt
 import org.mockito.Mock
@@ -155,9 +156,8 @@ class ClockEventControllerTest : SysuiTestCase() {
 
     @Test
     fun themeChanged_verifyClockPaletteUpdated() = runBlocking(IMMEDIATE) {
-        // TODO(b/266103601): delete this test and add more coverage for updateColors()
-        // verify(smallClockEvents).onRegionDarknessChanged(anyBoolean())
-        // verify(largeClockEvents).onRegionDarknessChanged(anyBoolean())
+         verify(smallClockEvents).onRegionDarknessChanged(anyBoolean())
+         verify(largeClockEvents).onRegionDarknessChanged(anyBoolean())
 
         val captor = argumentCaptor<ConfigurationController.ConfigurationListener>()
         verify(configurationController).addCallback(capture(captor))