Although this kind of lights are found in any store now, making one's own is quite satisfying.
The circuit works from 12 V power supply -- this goes to the strings of LEDs (4 in each string). The LM 7805 regulator makes voltage equal to 5 volts for the oscillators, so the frequency is not affected by supply voltage.
There are 4 strings of 4 LEDs, each string is its own colour (Red, Yellow, Green, Blue). The LEDs are driven by 2-transistor constant current sources (more info on them: https://www.merghart.com/p/27/Two-Transistor-laser-current-source). Currents through LED strings are adjusted so all colours are mostly the same brightness to eye.
Here is the circuit, annotated:
Multivibrators have slightly different frequencies, so the blinking patternt changes over time.
Video of the circuit operating:
This simple project took me less than a week from conception to completion, quite a refreshment from the last one.
Hope someone will be interested and maybe makes something similar.