Bees are not the only ones crazy about the blue indigo spires and the black and blue salvia. I also observe Annas hummingbirds sipping nectar from these plants. They tend to feed there in the morning and evening, while the bees and butterflies are on these plants during the day.
If you only get one kind of salvia plant you should get Blue Indigo Spires or Black and Blue Salvia. You'll have a lot of guests!