Here's a simple circuit diagram for a flashing light using an LED and a capacitor

      +--|>|--+
      |       |
      |      === C1
      |       |
      LED     |
      |       |
      +-------+
      |
     === R1
      |
     GND

Here are the components you will need:

• LED (any color)
• Capacitor (between 1uF and 100uF)
• Resistor (between 100 ohms and 1k ohms)
• Battery or power supply (DC voltage between 3V and 12V)

Here's how the circuit works:

1. When the power supply is turned on, the capacitor C1 starts to charge through the resistor R1.
2. As the capacitor charges, the voltage across it gradually increases.
3. When the voltage across the capacitor reaches the forward voltage of the LED, the LED turns on and the capacitor discharges through the LED.
4. As the capacitor discharges, the voltage across it decreases until it's no longer enough to keep the LED on.
5. When the LED turns off, the capacitor starts charging again and the cycle repeats.

The flashing rate of the LED can be adjusted by changing the values of the capacitor and resistor. A larger capacitor or a larger resistor will result in a slower flashing rate, while a smaller capacitor or a smaller resistor will result in a faster flashing rate.