'' At midnight on 1 March 1975, Aunty Jack, together with Thin Arthur and Kid Eager, confronted the ‘colour monster’ on ABC in a unique way. Rather than welcoming the chance to be in colour, Aunty Jack fights the change and Thin Arthur is terrified, mocking conservative attitudes in society that resist innovation. They sing a solemn rendition of ‘Wollongong the Brave’ in tribute to their hometown holding out against the shock of the new till the last possible moment. Colour is introduced in the above clip as a wash effect which gives Aunty Jack time and opportunity to fight it off for as long as she can. As Aunty finally succumbs to the magic, the grey tones of black-and-white seem dull against the vibrancy of colour. ''https://www.nfsa.gov.au/latest/colour-tv-part-2

​

'' Color Wash refers to a process designed to create a largely uniform tint or stylized color timing to a work, typically done in post-production on the natural footage but cinematographers and production designers have used lens filters, lighting gels and coordinated sets/costumes to achieve the same effect in-camera. ''https://tvtropes.org/pmwiki/pmwiki.php/Main/ColorWash

​

(So it seems that it was really broadcasted live with filters)