Here is a sample, when user click a button, it calls up function-HexToTColor,
and change the form color:
procedure TForm1.btnColorClick(Sender: TObject);
var
myColor:TColor;
begin
myColor:=HexToTColor('ffccdd');
form3.color:=myColor;
end;
function TForm1.HexToTColor(sColor : string) : TColor;
begin
Result :=
RGB(
StrToInt('$'+Copy(sColor, 1, 2)),
StrToInt('$'+Copy(sColor, 3, 2)),
StrToInt('$'+Copy(sColor, 5, 2))
);
end;