Richtext box aplhabets coloring problem

i used that but it is not help full

my code is

 internal void HighlightPhrase(RichTextBox box, string word, Color color)
        {      
           box.SuspendLayout();
   
            int pos = box.SelectionStart;
            string s = box.Text;
            int ix = 0;
            while (true)
            {
                int jx = s.IndexOf(phrase, ix, StringComparison.CurrentCultureIgnoreCase);
                if (jx < 0) break;
                box.SelectionStart = jx;
                box.SelectionLength = phrase.Length + 2;
                box.SelectionColor = color;
                ix = jx + 1;
            }
            box.SelectionStart = pos;
            box.SelectionLength = 0;
    box.ResumeLayout();
       
        }

HI

http://stackoverflow.com/questions/13220856/how-to-use-multi-color-in-richtextbox

http://www.dotnetperls.com/richtextbox

http://www.codeproject.com/Articles/37668/Multiple-Colored-Texts-in-RichTextBox-using-C