Who says Silver doesn't belong in a Colony game?
In a game with Lucky Coin and Merchant, I put Plan on Merchant. My Opponent didn't contest Merchant. Double Wharf as terminal secured +buy and enough coin to clear Colonies within 15 turns.
I mean, Silver's a fine card, even in Colony games. If you're going down the Treasure route Silver's still better than nothing in Colony games.
It makes no sense to me but WanderingWinder said it is true so I have always believed it to be true.
It's a money density thing. To buy Colony, you need $11. A hand of 5 Silvers generates $10. So adding Silver to your deck never helps you reach your desired money density. Of course that's less valid when you have lots of draw.
I don't think money density is the right way to look at this. Roughly, what you care about is how often you hit $11+, and money density only talking about the average doesn't express this super well.
If you assume that the only reasonable way to hit $11 is by drawing your Platinum, then the problem isn't how you hit $11, it's how you hit $6 from your non-Platinum treasures. So by buying Silver, you slightly slow down how often you get to see your Platinum, but you increase the odds that your non-Platinum treasures contribute to hitting $6, and my guess is that missing $11 is bad enough that you're okay with this tradeoff most of the time.