Recent weeks have seen Government House, on Upper Albert Road, swathed in scaffolding as renovations are undertaken ahead of Leung Chun-ying's move into the historic building. Over the years, most of Hong Kong's governors - and now, chief executives - have made alterations, additions or amendments to the official residence. Sir David Wilson, in office from 1987 to 92, added a charming garden pavilion, installed, according to legend, to counterbalance the baleful vibes emitted by the new Bank of China building on Garden Road. As I.M. Pei's distinctive modern landmark was widely believed to resemble a dagger pointed at the heart of Central - the whole story, taken within the context of its time, offers a striking architectural metaphor for jittery, pre-handover era Hong Kong. Let's hope that Wilson - a distinguished career diplomat who combined caution with genuine vision - got proper planning permission for his pavilion, and that illegal structures authorised by the city's top officials are only recent phenomena. The most widely known "addition" to Government House is actually an urban myth. There are several variants of the story that, during the wartime occupation, the Japanese added a tower to the residence. Government websites, including that of the Hong Kong Tourist Board, continue to propagate this fanciful tale. In fact, the Japanese pretty much rebuilt the entire building from scratch. From the earliest years, Government House was painted either white or a pale magnolia. Often forgotten today is that paint in the tropics was intended, first and foremost, as a preservative material, rather than having a decorative function. Early paints were supposed to retard mould and deter insects, and thus extend a building's expected lifespan. Whitewash, composed mainly of burnt limestone, was the main preparation used. The Pearl River estuary produced significant quantities of building lime in pre-European times, mostly gathered from coastal coral reefs. Kilns at Peng Chau, Chek Lap Kok and other locations bear witness to this early industry in Hong Kong. Added to the mix would be powdered sulphur, which - depending on the quantity used - produces a creamy, magnolia-like tint. Extra sulphur was sometimes added as an insecticide, mostly for use on buildings constructed of timber, to deter ants and termites. Attractive, lemon-coloured buildings, a common feature of Portuguese colonial cities from Macau to Brazil, principally owed their citrus hue to this addition. During Donald Tsang Yam-kuen's time in office, Government House was painted (on the advice, apparently, of a fung shui master), a dingy, tell-tale grey. A strikingly obvious metaphor for that administration's grubby legacy, the colour has now been replaced. Let's hope that Leung's return to a magnolia colour scheme augurs a return to (relatively speaking) cleaner days.