when you apply the "Professional" format in the designer, the plain grid view converts as below. Copy this and paste it into a skin file. Remove the ID="GridView1" This formatting gets applied to all GridViews.
<asp:GridView ID="GridView1" runat="server" CellPadding="4" ForeColor="#333333" GridLines="None">
<FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
<EditRowStyle BackColor="#999999" />
<SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
<PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
<HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<AlternatingRowStyle BackColor="White" ForeColor="#284775" />
</asp:GridView>
If you do not want it across all GridViews, the add SkinId="ProfessionalSkin" attribute, the set the GridView's SkinId property to "ProfessionalSkin"
<asp:GridView ID="GridView1" runat="server" CellPadding="4" ForeColor="#333333" GridLines="None" SkidId="ProfessionalSkin">
<FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
<EditRowStyle BackColor="#999999" />
<SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
<PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
<HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<AlternatingRowStyle BackColor="White" ForeColor="#284775" />
</asp:GridView>