<p>Set the <xref href="C1.Excel.XLStyle.BackColor" data-throw-if-not-resolved="false"></xref> property to <b>Color.Transparent</b> to

suppress this style element and use the default background color instead (white).

All colors on the C1XLBook are mapped to a palette. This means that if you assign colors to styles, save the book, and then load it back, you probably won't get exactly the same colors used when the book was created. You will get a fairly close approximation though.