With functions extracted.

gistfile1.cs

            set
            {
                Interaction.Info("View changed");
                var gridSettings = value ?? GridSettings.Default();
                _gridSettingsDispatcher.BookFilters = gridSettings.BookFilters;
                _gridSettingsDispatcher.SortDefinitions = gridSettings.SortDefinitions;
                _gridSettingsDispatcher.Grouping = gridSettings.Grouping;
                _gridSettingsDispatcher.ColumnPositions = gridSettings.ColumnPositions.Cast<IColumnDefinition>().ToList();
                _gridSettingsDispatcher.ColumnVisibility = SetDictionary(gridSettings.ColumnVisibilty, gridSettings);
                _gridSettingsDispatcher.ColumnWidths = SetDictionary(gridSettings.ColumnWidths, gridSettings);
                _gridSettingsDispatcher.ColumnFreezeIndex = gridSettings.ColumnFreezeIndex;
                _gridSettingsDispatcher.CurrentFilter = gridSettings.CurrentFilter;
                _gridSettingsDispatcher.GroupingColumnWidth = gridSettings.GroupingColumnWidth;
                _gridSettingsDispatcher.ForegroundDictionary = SetDictionary(gridSettings.ForegroundColors, gridSettings);
                _gridSettingsDispatcher.BackgroundDictionary = SetDictionary(gridSettings.BackgroundColors, gridSettings);
                _gridSettingsDispatcher.NegativeValuesRedDictionary = SetDictionary(gridSettings.NegativeValuesRed, gridSettings);
                _gridSettingsDispatcher.PositiveValuesBlueDictionary = SetDictionary(gridSettings.PositiveValuesBlue, gridSettings);
                _gridSettingsDispatcher.FormatStringsDictionary = SetDictionary(gridSettings.FormatString, gridSettings);
                _gridSettingsDispatcher.HideDefaultValuesDictionary = SetDictionary(gridSettings.HideDefaultValues, gridSettings); 
                _gridSettingsDispatcher.FireNeedsSaveChanged(this, false);
            }
        }

        private Dictionary<IColumnDefinition, bool> SetDictionary(Dictionary<string, bool> dictionary, GridSettings gridSettings)
        {
            return dictionary.Where(x => HasColumnDefinition(gridSettings.ColumnPositions, x.Key)).ToDictionary(x => FindColumnDefinition(gridSettings.ColumnPositions, x.Key), x => x.Value);
        }

        private Dictionary<IColumnDefinition, string> SetDictionary(Dictionary<string, string> dictionary, GridSettings gridSettings)
        {
            return dictionary.Where(x => HasColumnDefinition(gridSettings.ColumnPositions, x.Key)).ToDictionary(x => FindColumnDefinition(gridSettings.ColumnPositions, x.Key), x => x.Value);
        }

        private Dictionary<IColumnDefinition, Color> SetDictionary(Dictionary<string, Color> dictionary, GridSettings gridSettings)
        {
            return dictionary.Where(x => HasColumnDefinition(gridSettings.ColumnPositions, x.Key)).ToDictionary(x => FindColumnDefinition(gridSettings.ColumnPositions, x.Key), x => x.Value);
        }

        private Dictionary<IColumnDefinition, int> SetDictionary(Dictionary<string, int> dictionary, GridSettings gridSettings)
        {
            return dictionary.Where(x => HasColumnDefinition(gridSettings.ColumnPositions, x.Key)).ToDictionary(x => FindColumnDefinition(gridSettings.ColumnPositions, x.Key), x => x.Value);
        }

        private static bool HasColumnDefinition(List<ColumnDefinition> columns, string columnName)
        {
            if (columns == null || columnName == null) return false;
            return columns.Find(x => x.ColumnName.Equals(columnName))!=null;
        }

        internal static IColumnDefinition FindColumnDefinition(List<ColumnDefinition> columns, string columnName)
        {
            return columns.Find(x => x.ColumnName.Equals(columnName));
        }