setting gridview header back color

i am setting the gridview headers backcolor dynamically 
 if (!Page.IsPostBack)
            {         buildGrid();   gvTeamGameSeries.HeaderStyle.BackColor = Color.FromName("red"); }
 
however everytime i reload the page,backcolor disappears.If i move it out from IsPostBack block ,it works fine but i want to load grid only when the page loads for first time(inside !Page.IsPostBack).Whats the best way to handle this?thanks.

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