The light paint around the bogies is to do with crack detection in the stressed part of the bogies. Firstly, after cleaning the bogie in the affected area, a bright pink die (called the penetrant) is sprayed on. This is then wiped of and the white you see in the picture is sprayed on. If there are any cracks, the penetrant will have soaked into the cracks and re-appears as a line on the white. Estimated date.