Paddy – an interesting question!
I note that Stivcro (Post #2) observes that re-painting of the Common Property (building) MAY require a special resolution, and perhaps that’s because like me he/she thinks that it’s not all that clear.
My interpretation is that even if a proposed new colour scheme is a radical departure from what’s there now, the passing of an ordinary resolution at a General Meeting would suffice, as Sect 65A is intended to apply (although not so clearly) to structural changes that add to or alter the common property.
Even though painting too can “alter” the appearance of the building, that can if necessary be more easily reversed than those types of structural additions and alterations that I believe Sect 65A is intending to capture, so I agree with your Strata Manager.
Details of the proposed colour scheme must be distributed with the Agenda, and in order to obtain a more definitive vote you could call for a “poll” to determine that ordinary resolution on the basis of the units of entitlement of those Owners in attendance incl. by proxy (>50% to pass).