I played with a set of cards (Seaside + Prosperity) multiple times in a row. The setup was the same as well as the bot opponents.
In couple of games both Colony and Platinum cards were invisible and there were also no space for them.
#5282112 on tokyo. - invisible
#5282164 on frankfurt. - visible
#5282245 on frankfurt. - invisible
#5282307 on oregon. - visible
#5282614 on frankfurt. - visible
Browser Firefox ESR 52.2.1 (64-bit) on WIN 10
There are three settings for Colony/Platinum: Yes, No and Random.
The default is Random, and if you leave it at that it will choose a random card from your kingdom. If that randomly chosen card is from Prosperity it will use Colony/Platinum, and otherwise it doesn't.
Just to make sure...does the randomizer work also when there are Prosperity cards in the game meaning sometimes colonies/platimun are in and sometimes out?
Like in my games when I had exactly the same Prosperity and Seaside cards in every game?
yes