My mother has had dozens, every year. She has 6 feeders and fills them almost every day. In the evening, it is fun to watch them. It is almost like a war zone on her deck!
Do not use food coloring. Her receipt is 4 parts water, 1 part sugar. Boil the water, then add sugar. Once it is well dissolved, it cool for about an hour, then fill the feeders.
I have several feeders out with ribbon to attract them. I get 1-2 a week. I am not sure why but my neighbor who has had an incredible flower garden for years never gets them either. Lots of other birds, bees and wasps instead.