You don't need the red food coloring, they will find it if it has a red spot the size of a quarter. Once they know it's there, they'll come back every year...to the exact same spot. The food coloring has not been proven harmful, it's just not needed. The older red coloring was harmful, to humans as well as birds, the new type has not been proven harmful to the hummers.
Hummers will come back year after year and will remember exactly where your feeder is. Or was. That's how I've found out it was time to put out feeders a couple of times. Last spring I looked out the window and saw a hummer hovering within 6 inches of where the feeder was the previous summer. I had a feeder filled and hung a few minutes later, he had found it in 15 minutes.
Hummers are very territorial. One will always try to guard his favorite feeder, and I've seen females do the same. They will chase away any hummer that comes near, even their own offspring. It's a hereditary instinct. I've watched hummers try to guard two feeders.
They are also very tolerant of humans. If you sit near their feeder for about 10 minutes or so, they will finally start to come to it. In a while, they will pretty much ignore you. they are also attracted to red. I have a cap with a 2 inch red logo. I've seen hummers fly up and hover a foot in front of me, take a close look at it, then fly away at least a dozen times. They can also fly backwards and upside down to an extent.
Bluebirds will do the same, put up a nesting box and they will come back to the same location looking for it if it's been removed.
Mockingbirds...they follow your lawn mower looking for insects you just stirred up. They've been following my mowers for at least 20 years that I remember noticing it. Mockers are also much more tolerant of people than many birds. I watched one dive bomb my cat on a regular basis when I was in Louisiana. He also followed behind the mower to get bugs.
A couple of my pictures from last year. I haven't tried to get any this year. We usually only get Ruby Throated Hummingbirds here, I saw one Black Chinned Hummingbird in Louisiana. It was migrating, stayed for 3 days then left.
