Feeders come in different materials and in varying configurations. The hummingbirds will use all of them once they find out that there's nectar inside, but some feeders are much better than others. The most important quality is the ease of cleaning. Hummingbird feeders are filled with a solution that grows bacteria and mold even if left in a refrigerator long enough. In hot weather? That stuff grows VERY quickly. The especially dangerous black mold will begin growing as soon as one spore gets inside the feeder. And the spores are plentiful in the air outside. If you can't take apart your feeder, you can't see what's growing inside and you can't easily clean it.
Another thing to consider is the number of ports. If you only have a few birds, feeders with four ports are fine. Here in Studio City, I need feeders with ten ports, and even with 50 ports on the webcam, two birds will be often be sharing.
Feeders come in different materials. They may be metal, ceramic, plastic or glass. I use plastic because I have yet to find a glass feeder with a wide mouth making it easy to clean. AIso, I believe that the danger from mold is much bigger than the possible danger of BPA.
Most hummingbird feeders are red, because it is the number one color that attracts them. They don't have to be red, though. Once a hummer knows there is food inside, he/she will keep coming back. They will undoubtedly find the red feeders faster, though. The yellow flowers are pretty but unnecessary. Actually bees prefer yellow to red.
Feeders also come in two styles: saucer and vacuum. For a detailed description of both, click below.
Saucer vs. Vacuum Feeders