Color graphics function in windows forms

There are two problems, please suggest what is wrong:

1) Need to draw two graphs of functions. The functions are drawn, but in the same colors, although I also set colors in the 'Series' section in the chart parameters and using separate methods.

2) When you click on the solveButton button, the first function is drawn first and only after the second one is pressed again.

Code:

private void button1_Click(object sender, EventArgs e) { int n = Convert.ToInt32(nBox.Text); // кол-во точек(иксов) double[] xs = new double[n]; //иксы double[] fxs = new double[n]; //значение функции в иксе double[] result = new double[n]; // значение интерполированной функции for (int i = 0; i < n; i++) { xs[i] = (Math.PI / n) * (i + 1); fxs[i] = Function(xs[i]); result[i] = NDDP(xs[i], n, xs, fxs); chart1.Series["default"].Points.AddXY(xs[i], Function(xs[i])); chart1.Series["interpolated"].Points.AddXY(xs[i], result[i]); } }