When true, the standard Excel color palette will be used while exporting. Excel 97/2003 have only 53 available colors, and any color that does not match must be replaced with the nearest one. If this property is false, the Excel color palette will be changed to better display the real grid colors. Note that when you want to edit the generated file, having a custom palette might make it difficult to find the color you need.
Excel 2007 and newer support true color, so this property won't change how the generated files will display in Excel 2007. They will look fine no matter which option you choose.
property TExportOptions.UseExcelStandardColorPalette: Boolean