The colours 2 & 3 quoted by Dick are from a Dakin Memo dated March 42, no one knows the exact colours, they may have been close to the 507`s but could also have been something similar to MS? for your purpose the 507`s would suffice imoo.
There are several archived memo`s pertaining to the application of sky blue on the upper masts of RAN ships approx. mid 42, from that time through to wars end most RAN front line units were painted thus and can be seen in many images.
Sometimes the lighter upper masts are very difficult to distinguish and dependent on angle and other variables but trust me it was standard RAN application.
In many cases the official correspondence lagged the actual field applications and it is highly likely her masts were painted thus in late May 42, her upper masts were definitely sky blue in July, Sky Blue was white with a bluish hue as seen on Vladi`s model.
With respect to others who may have modelled Canberra, We had conducted a massive amount of research into her and Mr Karen`s model is the most accurate to date, other than his colours her layout would be identical for June/July.
He has used 5-N for overall, without going into it the colours applied to Canberra, Australia and part application of Hobart in late June/early July were mixed at G.I. from samples supplied from Chicago, The first references to Chicago Blue are dated early 43 but we know it was being applied from the 4th qtr of 42, there were several slightly different versions of C.B.