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Each Excel document has a single color palette that manages formatting colors and some drawing layer colors. A color palette contains 56 colors in Excel binary (.xls) format. Each of these colors may be customized, but changing a color in the palette will affect all formatting that uses the referenced color.
When ExcelWriter opens a workbook that does not contain an explicitly defined palette, or when ExcelWriter creates a new workbook, it uses the same default color palette that Excel uses. ExcelWriter never automatically adds colors to the palette.
Workbook.Palette returns a Palette object that represents the workbook's color palette. A Color object represents a single color in the palette.
To replace a color in the palette with a new color, call either of the following methods:
- This method takes the color to replace as a Color object, and the RGB values of the new color.
- This method takes the 0-based index of the color to replace, and the RGB values of the new color.
If you copy an object or cells with a custom color to another workbook, the custom color is replaced by the color in the corresponding position on the other workbook's color palette. To retain the custom color, either copy the customized color palette to the other workbook or change the corresponding color in the workbook.
If you are not sure that a specific color exists in the palette, and you want to assign the color to an element in the workbook, you can call Palette.GetClosestColor. Pass the method the red, green, and blue values of the ideal color. Palette.GetColor retrieves the color with the exact RGB value specified; if this color is not in the palette, an exception will be thrown.
A workbook's palette contains ten system colors that are fixed and cannot be changed by the user: SystemAutomaticFill, SystemAutomaticLine SystemBlack, SystemBlue, SystemCyan, SystemGreen, SystemMagenta, SystemRed, SystemWhite, and SystemYellow.
Drawing objects (pictures, shapes, comments, etc.) support custom RGB colors that may or may not be present in the palette. If you modify the color of an AutoShape (right-click the shape and select "Format AutoShape"), for example, and select a non-palette custom color, the change will not affect the workbook palette or other elements in the workbook to which the replaced color was assigned. To set custom values for shape fill and line colors, use Shape.SetCustomFillColor and Shape.SetCustomLineColor.