const int led_t = 360;
const int led_x = 100;
int[,] r_preview = new int[led_t,led_x];
int[,] g_preview = new int[led_t,led_x];
int[,] b_preview = new int[led_t,led_x];

//Assign some values to r_preview, g_preview, b_preview...

private void Send_LED_Data(object sender, SerialDataReceivedEventArgs e) //Function for serial LED communication
        {
            SerialPort sp = (SerialPort)sender;
            if (sp.ReadChar() == 'a')
            {
                byte[] data = new byte[3*led_x+1];
                data[0] = (byte)(c_interval);
                for (int i = 0; i < led_x; i++)
                {
                    data[i + 1] = (byte)(r_preview[index_of_array, i]);
                    data[i + led_x+1] = (byte)(g_preview[index_of_array, i]);
                    data[i + 2*led_x+1] = (byte)(b_preview[index_of_array, i]);
                }
                sp.Write(data, 0, 3*led_x+1);
                index_of_array=(index_of_array+1)%led_t;
            }
        }