diff --git a/Signal/src/ViewControllers/AppSettings/AdvancedSettingsTableViewController.m b/Signal/src/ViewControllers/AppSettings/AdvancedSettingsTableViewController.m
index 1b6ad314b..73d2902d5 100644
--- a/Signal/src/ViewControllers/AppSettings/AdvancedSettingsTableViewController.m
+++ b/Signal/src/ViewControllers/AppSettings/AdvancedSettingsTableViewController.m
@@ -195,6 +195,16 @@ NS_ASSUME_NONNULL_BEGIN
     }
     [contents addSection:censorshipSection];
 
+#ifdef THEME_ENABLED
+    OWSTableSection *themeSection = [OWSTableSection new];
+    themeSection.headerTitle = NSLocalizedString(@"THEME_SECTION", nil);
+    [themeSection addItem:[OWSTableItem switchItemWithText:NSLocalizedString(@"SETTINGS_ADVANCED_THEME", @"")
+                                                      isOn:[UIColor isThemeEnabled]
+                                                    target:weakSelf
+                                                  selector:@selector(didToggleThemeSwitch:)]];
+    [contents addSection:themeSection];
+#endif
+
     self.contents = contents;
 }
 
@@ -274,6 +284,13 @@ NS_ASSUME_NONNULL_BEGIN
     [self updateTableContents];
 }
 
+- (void)didToggleThemeSwitch:(UISwitch *)sender
+{
+    [UIColor setIsThemeEnabled:sender.isOn];
+
+    // TODO: Notify and refresh.
+}
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/Signal/translations/en.lproj/Localizable.strings b/Signal/translations/en.lproj/Localizable.strings
index d852ebce1..376104bab 100644
--- a/Signal/translations/en.lproj/Localizable.strings
+++ b/Signal/translations/en.lproj/Localizable.strings
@@ -1886,6 +1886,9 @@
 /* No comment provided by engineer. */
 "SETTINGS_ADVANCED_SUBMIT_DEBUGLOG" = "Submit Debug Log";
 
+/* No comment provided by engineer. */
+"SETTINGS_ADVANCED_THEME" = "Theme";
+
 /* No comment provided by engineer. */
 "SETTINGS_ADVANCED_TITLE" = "Advanced";
 
@@ -2132,6 +2135,9 @@
 /* Label for button to verify a user's safety number. */
 "SYSTEM_MESSAGE_ACTION_VERIFY_SAFETY_NUMBER" = "Verify Safety Number";
 
+/* No comment provided by engineer. */
+"THEME_SECTION" = "Theme";
+
 /* {{number of days}} embedded in strings, e.g. 'Alice updated disappearing messages expiration to {{5 days}}'. See other *_TIME_AMOUNT strings */
 "TIME_AMOUNT_DAYS" = "%@ days";
 
diff --git a/SignalMessaging/categories/UIColor+OWS.h b/SignalMessaging/categories/UIColor+OWS.h
index 419b20bc5..c51cf85b7 100644
--- a/SignalMessaging/categories/UIColor+OWS.h
+++ b/SignalMessaging/categories/UIColor+OWS.h
@@ -6,6 +6,10 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+#ifdef DEBUG
+#define THEME_ENABLED
+#endif
+
 @interface UIColor (OWS)
 
 #pragma mark - Global App Colors
@@ -77,6 +81,13 @@ NS_ASSUME_NONNULL_BEGIN
 @property (class, readonly, nonatomic) UIColor *ows_grey600Color;
 @property (class, readonly, nonatomic) UIColor *ows_darkSkyBlueColor;
 
+#pragma mark - Theme
+
+#ifdef THEME_ENABLED
++ (BOOL)isThemeEnabled;
++ (void)setIsThemeEnabled:(BOOL)value;
+#endif
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/SignalMessaging/categories/UIColor+OWS.m b/SignalMessaging/categories/UIColor+OWS.m
index 3c979ad8c..3b6e0e7da 100644
--- a/SignalMessaging/categories/UIColor+OWS.m
+++ b/SignalMessaging/categories/UIColor+OWS.m
@@ -2,12 +2,17 @@
 //  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
 //
 
-#import "UIColor+OWS.h"
 #import "OWSMath.h"
+#import "UIColor+OWS.h"
 #import <SignalServiceKit/Cryptography.h>
+#import <SignalServiceKit/OWSPrimaryStorage.h>
+#import <SignalServiceKit/YapDatabaseConnection+OWS.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
+NSString *const UIColorCollection = @"UIColorCollection";
+NSString *const UIColorKeyThemeEnabled = @"UIColorKeyThemeEnabled";
+
 @implementation UIColor (OWS)
 
 #pragma mark - Global App Colors
@@ -338,6 +343,26 @@ NS_ASSUME_NONNULL_BEGIN
     return [self.ows_conversationColorMap allKeysForObject:color].firstObject;
 }
 
+#pragma mark - Theme
+
++ (BOOL)isThemeEnabled
+{
+    OWSAssertIsOnMainThread();
+
+    return [OWSPrimaryStorage.sharedManager.dbReadConnection boolForKey:UIColorKeyThemeEnabled
+                                                           inCollection:UIColorCollection
+                                                           defaultValue:NO];
+}
+
++ (void)setIsThemeEnabled:(BOOL)value
+{
+    OWSAssertIsOnMainThread();
+
+    [OWSPrimaryStorage.sharedManager.dbReadWriteConnection setBool:value
+                                                            forKey:UIColorKeyThemeEnabled
+                                                      inCollection:UIColorCollection];
+}
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/SignalMessaging/utils/OWSPreferences.h b/SignalMessaging/utils/OWSPreferences.h
index fca6588f2..15c653f38 100644
--- a/SignalMessaging/utils/OWSPreferences.h
+++ b/SignalMessaging/utils/OWSPreferences.h
@@ -61,8 +61,6 @@ extern NSString *const OWSPreferencesCallLoggingDidChangeNotification;
 - (BOOL)hasGeneratedThumbnails;
 - (void)setHasGeneratedThumbnails:(BOOL)value;
 
-#pragma mark - Calling
-
 #pragma mark Callkit
 
 - (BOOL)isSystemCallLogEnabled;
diff --git a/SignalMessaging/utils/OWSPreferences.m b/SignalMessaging/utils/OWSPreferences.m
index b9ef59659..9484812df 100644
--- a/SignalMessaging/utils/OWSPreferences.m
+++ b/SignalMessaging/utils/OWSPreferences.m
@@ -58,7 +58,7 @@ NSString *const OWSPreferencesKeySystemCallLogEnabled = @"OWSPreferencesKeySyste
     OWSAssert(key != nil);
 
     __block id result;
-    [OWSPrimaryStorage.dbReadConnection readWithBlock:^(YapDatabaseReadTransaction *_Nonnull transaction) {
+    [OWSPrimaryStorage.dbReadConnection readWithBlock:^(YapDatabaseReadTransaction *transaction) {
         result = [self tryGetValueForKey:key transaction:transaction];
     }];
     return result;
@@ -72,10 +72,9 @@ NSString *const OWSPreferencesKeySystemCallLogEnabled = @"OWSPreferencesKeySyste
 
 - (void)setValueForKey:(NSString *)key toValue:(nullable id)value
 {
-    [OWSPrimaryStorage.dbReadWriteConnection
-        readWriteWithBlock:^(YapDatabaseReadWriteTransaction *_Nonnull transaction) {
-            [self setValueForKey:key toValue:value transaction:transaction];
-        }];
+    [OWSPrimaryStorage.dbReadWriteConnection readWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {
+        [self setValueForKey:key toValue:value transaction:transaction];
+    }];
 }
 
 - (void)setValueForKey:(NSString *)key