You can define data sorting for the report via XML configuration.
<hierarchy sort="desc">Possible values:
<dimensionName>[Color]</dimensionName>
<hierarchyName>[Color].[Color]</hierarchyName>
</hierarchy>
<axis name="rows">
<hierarchy>
<dimensionName>[Color]</dimensionName>
<hierarchyName>[Color].[Color]</hierarchyName>
</hierarchy>
<hierarchy>
<dimensionName>[Category]</dimensionName>
<hierarchyName>[Category].[Category]</hierarchyName>
</hierarchy>
<sort tuple="[Color].[Color].[red], [Category].[Category].[Cars]" measure="[Measures].[Price]">desc</sort>
</axis>