diff --git a/ClosedXML/Excel/Style/XLFillKey.cs b/ClosedXML/Excel/Style/XLFillKey.cs
index c2f2495..181b223 100644
--- a/ClosedXML/Excel/Style/XLFillKey.cs
+++ b/ClosedXML/Excel/Style/XLFillKey.cs
@@ -15,17 +15,33 @@
             var hashCode = 2043579837;
             hashCode = hashCode * -1521134295 + BackgroundColor.GetHashCode();
             hashCode = hashCode * -1521134295 + PatternColor.GetHashCode();
-            hashCode = hashCode * -1521134295 + PatternType.GetHashCode();
+
+            var patternType = PatternType;
+            if (BackgroundColor.ColorType == XLColorType.Indexed && BackgroundColor.Indexed == 64)
+                patternType = XLFillPatternValues.None;
+
+            hashCode = hashCode * -1521134295 + patternType.GetHashCode();
+
             return hashCode;
         }
 
         public bool Equals(XLFillKey other)
         {
-            return
-                (PatternType == XLFillPatternValues.None && other.PatternType == XLFillPatternValues.None) ||
-                BackgroundColor == other.BackgroundColor
-             && PatternColor == other.PatternColor
-             && PatternType == other.PatternType;
+            if (PatternType == XLFillPatternValues.None && other.PatternType == XLFillPatternValues.None)
+                return true;
+
+            var patternType1 = PatternType;
+            var patternType2 = other.PatternType;
+
+            if (BackgroundColor.ColorType == XLColorType.Indexed && BackgroundColor.Indexed == 64)
+                patternType1 = XLFillPatternValues.None;
+
+            if (other.BackgroundColor.ColorType == XLColorType.Indexed && other.BackgroundColor.Indexed == 64)
+                patternType2 = XLFillPatternValues.None;
+
+            return BackgroundColor == other.BackgroundColor
+                   && PatternColor == other.PatternColor
+                   && patternType1 == patternType2;
         }
 
         public override bool Equals(object obj)
diff --git a/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/Excel/XLWorkbook_Save.cs
index 52e2211..74edc65 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -3982,7 +3982,8 @@
                                 break;
                         }
 
-                        patternFill.AppendChild(backgroundColor);
+                        if (backgroundColor.HasChildren)
+                            patternFill.AppendChild(backgroundColor);
                     }
                     else
                     {
@@ -3995,7 +3996,11 @@
                                 break;
 
                             case XLColorType.Indexed:
-                                foregroundColor.Indexed = (UInt32)fillInfo.Fill.BackgroundColor.Indexed;
+                                // 64 is 'transparent' and should be ignored for differential formats
+                                if (fillInfo.Fill.BackgroundColor.Indexed != 64)
+                                    foregroundColor.Indexed = (UInt32)fillInfo.Fill.BackgroundColor.Indexed;
+
+                                //foregroundColor.Indexed = (UInt32)fillInfo.Fill.BackgroundColor.Indexed;
                                 break;
 
                             case XLColorType.Theme:
@@ -4007,7 +4012,8 @@
                                 break;
                         }
 
-                        patternFill.AppendChild(foregroundColor);
+                        if (foregroundColor.HasChildren)
+                            patternFill.AppendChild(foregroundColor);
                     }
                     break;
 
@@ -4033,7 +4039,8 @@
                             break;
                     }
 
-                    patternFill.AppendChild(foregroundColor);
+                    if (foregroundColor.HasChildren)
+                        patternFill.AppendChild(foregroundColor);
 
                     backgroundColor = new BackgroundColor();
                     switch (fillInfo.Fill.BackgroundColor.ColorType)
@@ -4055,14 +4062,19 @@
                             break;
                     }
 
-                    patternFill.AppendChild(backgroundColor);
+                    if (backgroundColor.HasChildren)
+                        patternFill.AppendChild(backgroundColor);
 
                     break;
             }
 
-            fill.AppendChild(patternFill);
+            if (patternFill.HasChildren)
+                fill.AppendChild(patternFill);
 
-            return fill;
+            if (fill.HasChildren)
+                return fill;
+            else
+                return null;
         }
 
         private bool FillsAreEqual(Fill f, XLFillValue xlFill, Boolean fromDifferentialFormat)