The black, red, green and yellow colours of the navigation buoys remained in chromaticity regions according to IALA Recommendation E-108 – Surface colours used as visual signals on aids to navigation, Edition 3, 2013.
You will find the presentation here (Youtube 1:35).
The visual appearance of the colours was however changed due to changes in gloss and/or lightness of the colour that are not taken into account in the IALA Recommendation for chromaticity regions.
The test specimens, plastic material samples of navigation buoys, in colours black, red, green and yellow, were exposed to solar radiation until an UV-energy dose, which corresponds to at least 23 years in natural conditions on vertical surfaces, was reached.
The exposure in this test consists of two parts.
Exposure 1
Solar radiation exposure (UV+vis+IR)
Intensity of radiation: 1120 W/m2
T(Amb): ~40℃
Cycle: 22 h solar irradiation / 2 h water spray or high RH (salt mist spray weekly)
Duration: 56 days
Test conditions based on ISO 4892-1 and MIL-STD-810G METHOD 505.5
Exposure 2
High-intensity solar radiation exposure (UV+Vis+IR)
Intensity of radiation: Continuous high-intensity radiation (3500 W/m2 with sample cooling)
T(Amb): ~30℃
Duration: until reaching an UV-energy dose that corresponds to at least of 15 years in natural conditions on vertical surfaces
Measurements
Chromaticity coordinate zone analysis
Colour CIELAB1976 and DE (colour change)