I do not know for sure, but I have seen aphids of varying colors depending on their habitat. Maybe they even change color depending on what kind of sap they are sipping. I am no expert though. But if it looks like an aphid, it probably is an aphid. Is is attached to the plant siphoning off the sap? Again, if it looks like an aphid and acts like an aphid . . . There's a lot of diversity in the insect group! I Googled "blue aphid" and came up with a lot of interesting hits! There's a pea/alfalfa aphid, and I know lupines are in the legume family too (as are peas and alfalfa), so it stands to reason they would have similar pests.

Thanks so much for your info. I think you are correct. I had no idea there were so many kinds of aphids! When my husband first saw them he said there were so many of them he couldn't see the flowers. They were sucking the "juice' out of the plant so fiercely that the leaves were wilted. After spraying for a few days they were all gone and didn't return.