diff --git a/src/client/graphics/layers/TerritoryLayer.ts b/src/client/graphics/layers/TerritoryLayer.ts
index ce1b9a705..fd3f520ed 100644
--- a/src/client/graphics/layers/TerritoryLayer.ts
+++ b/src/client/graphics/layers/TerritoryLayer.ts
@@ -267,15 +267,13 @@ export class TerritoryLayer implements Layer {
           )
           .filter((u) => u.unit.owner() == owner).length > 0
       ) {
-        const useDefendedBorderColor = playerIsFocused
-          ? this.theme.focusedDefendedBorderColor()
-          : this.theme.defendedBorderColor(owner);
-        this.paintCell(
-          this.game.x(tile),
-          this.game.y(tile),
-          useDefendedBorderColor,
-          255,
-        );
+        const borderColors = this.theme.defendedBorderColors(owner);
+        const x = this.game.x(tile);
+        const y = this.game.y(tile);
+        const lightTile =
+          (x % 2 == 0 && y % 2 == 0) || (y % 2 == 1 && x % 2 == 1);
+        const borderColor = lightTile ? borderColors.light : borderColors.dark;
+        this.paintCell(x, y, borderColor, 255);
       } else {
         const useBorderColor = playerIsFocused
           ? this.theme.focusedBorderColor()
diff --git a/src/core/configuration/Config.ts b/src/core/configuration/Config.ts
index 9f55f8b52..93e2f54c9 100644
--- a/src/core/configuration/Config.ts
+++ b/src/core/configuration/Config.ts
@@ -143,9 +143,8 @@ export interface Theme {
   territoryColor(playerInfo: PlayerView): Colord;
   specialBuildingColor(playerInfo: PlayerView): Colord;
   borderColor(playerInfo: PlayerView): Colord;
-  defendedBorderColor(playerInfo: PlayerView): Colord;
+  defendedBorderColors(playerInfo: PlayerView): { light: Colord; dark: Colord };
   focusedBorderColor(): Colord;
-  focusedDefendedBorderColor(): Colord;
   terrainColor(gm: GameMap, tile: TileRef): Colord;
   backgroundColor(): Colord;
   falloutColor(): Colord;
diff --git a/src/core/configuration/PastelTheme.ts b/src/core/configuration/PastelTheme.ts
index 9c4ac5d6c..8218268be 100644
--- a/src/core/configuration/PastelTheme.ts
+++ b/src/core/configuration/PastelTheme.ts
@@ -98,21 +98,17 @@ export const pastelTheme = new (class implements Theme {
       b: Math.max(tc.b - 40, 0),
     });
   }
-  defendedBorderColor(player: PlayerView): Colord {
-    const bc = this.borderColor(player).rgba;
-    return colord({
-      r: Math.max(bc.r - 40, 0),
-      g: Math.max(bc.g - 40, 0),
-      b: Math.max(bc.b - 40, 0),
-    });
+
+  defendedBorderColors(player: PlayerView): { light: Colord; dark: Colord } {
+    return {
+      light: this.territoryColor(player).darken(0.2),
+      dark: this.territoryColor(player).darken(0.4),
+    };
   }
 
   focusedBorderColor(): Colord {
     return colord({ r: 230, g: 230, b: 230 });
   }
-  focusedDefendedBorderColor(): Colord {
-    return colord({ r: 200, g: 200, b: 200 });
-  }
 
   terrainColor(gm: GameMap, tile: TileRef): Colord {
     const mag = gm.magnitude(tile);
diff --git a/src/core/configuration/PastelThemeDark.ts b/src/core/configuration/PastelThemeDark.ts
index bc9dd8ddf..f1d52c824 100644
--- a/src/core/configuration/PastelThemeDark.ts
+++ b/src/core/configuration/PastelThemeDark.ts
@@ -98,21 +98,17 @@ export const pastelThemeDark = new (class implements Theme {
       b: Math.max(tc.b - 40, 0),
     });
   }
-  defendedBorderColor(player: PlayerView): Colord {
-    const bc = this.borderColor(player).rgba;
-    return colord({
-      r: Math.max(bc.r - 40, 0),
-      g: Math.max(bc.g - 40, 0),
-      b: Math.max(bc.b - 40, 0),
-    });
+
+  defendedBorderColors(player: PlayerView): { light: Colord; dark: Colord } {
+    return {
+      light: this.territoryColor(player).darken(0.2),
+      dark: this.territoryColor(player).darken(0.4),
+    };
   }
 
   focusedBorderColor(): Colord {
     return colord({ r: 255, g: 255, b: 255 });
   }
-  focusedDefendedBorderColor(): Colord {
-    return colord({ r: 215, g: 215, b: 215 });
-  }
 
   terrainColor(gm: GameMap, tile: TileRef): Colord {
     const mag = gm.magnitude(tile);