The highlighted verb (Straits Times Life!, 9 September 2011) would probably have English teachers reaching for their red pens. The correct form is the singular has, rather than plural have, because the verb should agree with the head noun, collection, and not the nearest noun, watercolours.
Incidentally, in British English the name Farquhar is pronounced /ˈfɑːkə/ or /ˈfɑːkwə/. However, most Singaporeans who have attended English-medium schools will remember having been taught the pronunciation /ˈfɑːkwɑː/. Considering that Singaporeans generally make no distinction between /ʌ/ and /ɑː/, insisting on using the British pronunciation for this British name would probably be ill advised.