private void panelColor_DoubleClick(object sender, EventArgs e)
{
using (var dialog = new ColorChooserForm())
{
dialog.AlphaEnabled = false;
Color c = this.panelColor.BackColor;
dialog.Color = Color.FromArgb(255, c.R, c.G, c.B);
if (dialog.ShowDialog() == DialogResult.OK)
this.panelColor.BackColor = dialog.Color;
}
}