To start the call a Skype, Process.Start("callto:john");. You can associate "callto:" with the name of the contact.
MSDN # , , . , , - "".
Choices colors = new Choices();
colors.Add(new string[] {"red", "green", "blue"});
GrammarBuilder gb = new GrammarBuilder();
gb.Append(colors);
Grammar g = new Grammar(gb);
UPDATE
Skype4comLib. !
Skype skype;
skype = new SKYPE4COMLib.Skype();
string SkypeID = "john";
Call call = skype.PlaceCall(SkypeID);