Epsom salts has no effect on flower color. And with a few, very limited exceptions, flower color is not influenced by soil chemistry or amendments. Unless the amendment is food color :-)

The color is not usually a problem if you have enough plants and enough flowers. A skimpy planting just looks, well skimpy! Al

Thanks for the information. I guess I'll just enjoy them as they are. Last year was the first year I had flowers and it looks like this year I'll have even more. I won't fool with mother nature!

It's probably just the variety you have: some are naturally mid-blue. Suggest you might want to look around for darker varieties- something like 'Gael's Sapphire', perhaps.