Now this may just be coincidence, but I did find it interesting that different colored bees were attracted to different colored flowers. Use the magnifyier for a closer examination.
I think they Do have certain flowers they are attracted to. Overall, I feel like bumble and carpenter bees prefer purple flowers. They always seem to be on purple!
That's interesting and you might be on to something there because I don't think I've ever seen the yellow bees on my Coneflowers either. But I have seen them on the yellow and red ones. Nice collage!