My opponent tried that against me once. He had a few sapphire mines and got all the sapphire chips. So I ended up being on Blue lock down for several turns save for yellow chips from reserving. But luck was on my side when my opponent purchased a card as it was replaced by a sapphire mine that I immediately snagged up.
Had that sapphire card not showed up when it did, my opponent could have had a big lead as blue was vital to most of the board.
This is what happened to me after I got a couple of cards that needed lots of blue gems. He managed to keep them out of my hands for most of the game and won.