Googling around I don't see writings about visual attraction to shapes or patterns or ultraviolet. I do see that while the birds can see well into the ultraviolet, so do most insects, so you can attract more relatively more hummers than insects with red, as the latter don't do well in that range.

My preference is agapanthus (light blue, long bloom, very hardy), because I have an aversion to feeders, just as I wouldn't feed Kool-Aid to my kids. (None of the professionals seem to share this aversion.)

But this interesting page says that different plants are more attractive to the hummers in different regions.