diff --git a/packages/rn-tester/js/examples/Playground/RNTesterPlayground.js b/packages/rn-tester/js/examples/Playground/RNTesterPlayground.js
index 8e6b10479de7..e8b7f2865561 100644
--- a/packages/rn-tester/js/examples/Playground/RNTesterPlayground.js
+++ b/packages/rn-tester/js/examples/Playground/RNTesterPlayground.js
@@ -10,24 +10,135 @@
 
 import type {RNTesterModuleExample} from '../../types/RNTesterTypes';
 
-import RNTesterText from '../../components/RNTesterText';
 import * as React from 'react';
-import {StyleSheet, View} from 'react-native';
+import {useEffect, useState} from 'react';
+import {
+  Appearance,
+  Button,
+  DynamicColorIOS,
+  StyleSheet,
+  Text,
+  useColorScheme,
+  View,
+} from 'react-native';
+
+// Reproducer for https://github.com/facebook/react-native/issues/57836
+//
+// ONE dynamic color, used for both fills and borders:
+// red in light mode, green in dark mode.
+//
+// Run RNTester on iOS with the simulator's System Appearance set to LIGHT,
+// then open this Playground example. The demo forces the app dark via
+// Appearance.setColorScheme('dark') after 2s and mounts a second row of
+// boxes at 4s.
+//
+// Expected: once the app is dark, every fill and border is green.
+// Actual: fills turn green, but the borders of row A (mounted before the
+// override) stay red — the light variant — on both border code paths
+// (border-image and CoreAnimation), and persist indefinitely.
+const dynamicColor = DynamicColorIOS({light: '#ff3b30', dark: '#34c759'});
+
+function Boxes({label}: {label: string}) {
+  return (
+    <View style={styles.section}>
+      <Text style={styles.sectionLabel}>{label}</Text>
+      <View style={styles.row}>
+        <View style={[styles.box, {backgroundColor: dynamicColor}]}>
+          <Text style={styles.boxLabel}>fill</Text>
+        </View>
+        <View
+          style={[styles.box, styles.bordered, {borderColor: dynamicColor}]}>
+          <Text style={styles.boxLabel}>border{'\n'}(image path)</Text>
+        </View>
+        <View
+          style={[
+            styles.box,
+            styles.bordered,
+            styles.clipped,
+            {borderColor: dynamicColor},
+          ]}>
+          <Text style={styles.boxLabel}>border{'\n'}(CA path)</Text>
+        </View>
+      </View>
+    </View>
+  );
+}
+
+function Run() {
+  const scheme = useColorScheme();
+  const [afterOverride, setAfterOverride] = useState(false);
+  const [phase, setPhase] = useState('phase 0: system appearance');
+
+  useEffect(() => {
+    // Phase 1: the app forces dark while the SYSTEM stays light
+    // (RCTAppearance sets overrideUserInterfaceStyle on every window).
+    const t1 = setTimeout(() => {
+      Appearance.setColorScheme('dark');
+      setPhase('phase 1: setColorScheme("dark"), system still Light');
+    }, 2000);
+    // Phase 2: mount a second set of boxes while the override is active.
+    const t2 = setTimeout(() => {
+      setAfterOverride(true);
+      setPhase('phase 2: second row mounted under the dark override');
+    }, 4000);
+    return () => {
+      clearTimeout(t1);
+      clearTimeout(t2);
+    };
+  }, []);
+
+  return (
+    <View>
+      <Text style={styles.title}>useColorScheme(): {String(scheme)}</Text>
+      <Text style={styles.subtitle}>{phase}</Text>
+      <Boxes label="A: mounted BEFORE the dark override" />
+      {afterOverride && <Boxes label="B: mounted AFTER the dark override" />}
+      <Text style={styles.footer}>
+        Expected: every fill and border shows the SAME color (green once the
+        app is dark). Bug: row A's borders stay red — the system (light)
+        variant — while its fill turns green.
+      </Text>
+    </View>
+  );
+}
 
 function Playground() {
+  const [runId, setRunId] = useState(0);
   return (
-    <View style={styles.container}>
-      <RNTesterText>
-        Edit "RNTesterPlayground.js" to change this file
-      </RNTesterText>
+    <View style={styles.screen}>
+      <Run key={runId} />
+      <Button
+        title="Reset to system scheme & run again"
+        onPress={() => {
+          Appearance.setColorScheme(null);
+          setRunId(id => id + 1);
+        }}
+      />
     </View>
   );
 }
 
 const styles = StyleSheet.create({
-  container: {
-    padding: 10,
+  screen: {
+    padding: 16,
+    backgroundColor: '#202124',
+  },
+  title: {fontSize: 18, fontWeight: '600', color: '#fff'},
+  subtitle: {fontSize: 13, color: '#bbb', marginTop: 4, marginBottom: 8},
+  section: {marginTop: 12},
+  sectionLabel: {fontSize: 14, color: '#fff', marginBottom: 8},
+  row: {flexDirection: 'row', gap: 12},
+  clipped: {overflow: 'hidden'},
+  box: {
+    width: 100,
+    height: 76,
+    alignItems: 'center',
+    justifyContent: 'center',
+    borderRadius: 8,
   },
+  bordered: {borderWidth: 6},
+  boxLabel: {color: '#fff', fontSize: 12, textAlign: 'center'},
+  footer: {marginVertical: 16, fontSize: 12, color: '#999', lineHeight: 17},
 });
 
 export default {