diff --git a/src/Program.cs b/src/Program.cs
index 278d331..948c398 100644
--- a/src/Program.cs
+++ b/src/Program.cs
@@ -212,6 +212,13 @@ namespace Palettizer
 					else
 					{
                         palette.AddColor(color);
+
+						var grayscaleColor = palette.ColorToGrayscaleMap[color];
+
+						grayscaleImage[i] = grayscaleColor;
+						grayscaleImage[i + 1] = grayscaleColor;
+						grayscaleImage[i + 2] = grayscaleColor;
+						grayscaleImage[i + 3] = color.A;
 					}
 				}
 			}