'Amber' - you could have heard a NATO airfield 'colour state', which range from 'BLUE' (Blue Sky'ish) via WHITE/GREEN/YELLOW/AMBER to 'RED' (not nice - ie below CAT 1 limits) to 'BLACK' - someone or something has closed the airfield. The RAF USED to have 'YELLOW1 and YELLOW2 in my days (post Spitfire
)