You need to access options to change a dimension's color palette.

 You can use the Color legend to access options to change a dimension’s color palette, in addition to the Marks card. The Color legend shows the colors assigned to each member of the dimension in the view. You can right-click on the Color legend and select Edit Colors to open the Edit Colors dialog box, where you can change the color palette, assign specific colors to dimension members, or edit the color transparency and border6 The other options are not valid ways to change a dimension’s color palette. Edit in Shelf is a feature that allows you to edit the fields on the Rows or Columns shelves by typing directly on the shelf. It does not affect the color palette of the dimension7 The Format menu allows you to change the appearance of various elements in the workbook, such as fonts, borders, shading, alignment, etc. It does not have options for changing the color palette of the dimension8 Edit Caption is a feature that allows you to add or edit a caption for a worksheet or dashboard. It does not affect the color palette of the dimension