//timer interval = 1000
        public int flag = 0;
        private void timer1_Tick(object sender, EventArgs e)
        {
            switch (flag)
            {
                case 0:
                    label1.ForeColor = Color.Red;
                    flag = 1;
                    break;
                case 1:
                    label1.ForeColor = Color.PowderBlue;
                    flag = 2;
                    break;
                case 2:
                    label1.ForeColor = Color.RosyBrown;
                    flag = 3;
                    break;
                case 3:
                    label1.ForeColor = Color.Black;
                    flag = 4;
                    break;
                case 4:
                    label1.ForeColor = Color.PaleGreen;
                    flag = 0;
                    break;                    
            }            
        }