To pop up color picker to pick color from in windows forms Add this code in some event to get that.
Color clr = Color.FromArgb(255, 255, 255);
System.Windows.Forms.ColorDialog colorDlg = new System.Windows.Forms.ColorDialog();
colorDlg.Color = clr;
if (colorDlg.ShowDialog() == DialogResult.OK)
{
clr = colorDlg.Color;
}