GridView Dropdownlist CSS First letter should be black color and remaining content should be in green color

GridView Dropdownlist CSS First letter should be black color and remaining
content should be in green color

how do i change the color of a first letter in dropdownlist inside gridview?
<asp:GridView ID="grdAvailableRooms" runat="server" >
<Columns>
<asp:TemplateField HeaderText="TESTDROPDOWN">
<ItemTemplate>
<asp:DropDownList ID="ddlRoomsCount" runat="server"
Width="120px"CssClass="GridTextinGreen" >
<asp:ListItem Value="0">Day</asp:ListItem>
<asp:ListItem Value="1">1 (USD 3510)</asp:ListItem>
<asp:ListItem Value="2">2 (SAR 7020)</asp:ListItem>
<asp:ListItem Value="3">3 (USD 8610)</asp:ListItem>
<asp:ListItem Value="4">4 (SAR 9050)</asp:ListItem>
</asp:DropDownList>
<Columns>
</asp:GridView>
eg: 1 (USD 3510)- the first letter '1' should be display in Black Color
and the remaining content should be display in Green Color
Pls help me to apply these type of style.