ICAO Annex 14 regulation, for unmarked structures (unpainted with white / red horizontal bands), prescribes the use of Aircraft Warning Lights both day and night operation.
Appendix 6-7 of the standard indicates the use of two types of obstacle warning lights: high intensity HIOL-AB white flashing in day and twilight mode (200.000cd - 20.000cd) which turns red flashing in night mode (2.000cd) and low intensity red color steady burning in night mode (LIOL-B 32cd). High intensity AWLs must be placed on the top of the structure, and the underlying levels must respect the alternation between high and low intensity beacons.
For example, for a structure with a total height of 190 meters 4 levels of lights must be installed: the one at the top and the second with high intensity beacons and the third one and the lower one with low intensity beacons. Moreover, if on the structure there are antennas or thin structures higher than 12 meters, on these structures it will be necessary to install medium intensity AB lights (white flashing 20.000cd during the day and red 2.000cd at night).
If an aeronautical study or the civil aviation body under which the control of the structure in question falls, decides the use of other lights or other configurations, the prescriptions must be respected by way of derogation from the ICAO standard Annex 14.