In the picture below, you can see a schematic diagram of a simple LED flasher with two popular NE555 ICs.

Step 1: LED Flasher Circuit With Two NE555 Chips

Both 555s operate as an unstable flip-flop, each with a different frequency. Their outputs are connected in anti-parallel two groups of LEDs. The frequency and character of the flashing can be adjusted by changing the values of C2, C3, R2 and R3.

R3 and C3 affect the flash rate, R2 and C2 affect the color switching rate.

You can also use a different number and color of LEDs, but you need to adjust the value of R1 to not exceed the maximum LED current. The current must also not exceed the maximum output current of the 555 circuit, which is 200mA. The circuit can be powered from any 12V source (9-15V).

Below is a list of items:

Chip NE555 - 2 pcs.
Red LED - 4 pcs.
Blue LED - 4 pcs.
Capacitor 100 uF x 25V - 1 pc.
Capacitor 1uF x 50V - 1 pc.
Capacitor 100nF - 1 pc.
1MΩ resistor - 2 pcs.
Resistor 270 Ohm - 1 pc.
Battery block - 1 pc.
Battery 9V - 1 pc.
Wire for the frame with a diameter of 0.8 mm and 0.5 mm

Below are photos of the flasher assembly option.