Did Collingwood go to black and white as other Association clubs already used Brittania's red, white and blue?
Yes.
The VFA were just starting to get strict on what colours clubs could wear.
And Footscray was Red, White & Blue.
But Collingwood, being a new club, were open to choosing anything as their colours. Anything, except what was already in use.
Britannia were a club that played at Victoria Park, along with a few others in the local football comp.
When Collingwood formed many of the Britannia players and officials joined the new club. But then, many of them joined Fitzroy at the same time.
The link between Britannia and Collingwood is tenuous, and people seem to make more or less of that link depending on how it suits their argument at the time.
Yes, Britannia did wear Blue & White hoops with a Red sash, and while these would have been ideal for Collingwood, given they wouldn't have had to buy jumpers, they would not have been allowed to wear those colours in the VFA.
Later, Hawthorn joined the VFA and were made to change from their Gold & Blue to Gold & Brown.
As mentioned earlier, the colours and design were apparently introduced after seeing them used by South Australia as their state jumpers.