将16进制（HTML）颜色值转换成 Color类型
private void btnChangeColor_Click(object sender, EventArgs e)
{
txtColor.BackColor = ColorTranslator.FromHtml("#99FF00");
txtColor.Text = "#99FF00";
}
private void btnChangeColor_Click(object sender, EventArgs e)
{
txtColor.BackColor = ColorTranslator.FromHtml("#99FF00");
txtColor.Text = "#99FF00";
}