Here is the article that Hu is criticizing:

Hummingbirds, Canaries in the Coal Mine

By STEVE ARGUE
Red dye number 40, an azo dye made from coal tar, is found in human food and fed to hummingbirds in food mixes sold by Perky-Pet.

The idea of mixing red dye with sugar, and then upping the price to market it as a special food for hummingbirds is no doubt profitable for Perky-Pet and the manufacturers of red dye number 40, but what is the impact on hummingbirds? No controlled studies have been done to find out if the dye is safe for hummingbirds. In addition, strong anecdotal information from experienced wildlife rehabilitators indicates that the dye is harmful. They have found a disturbing rate of tumors on the bills and liver damage in hummingbirds that were known to feed on dyed sugar water.

Red dye number 40 is also fed to humans with the approval of the FDA; this does not mean it is safe for hummingbirds or even humans.

A good example of how chemicals react differently in the bodies of different organisms is the chemical acetaminophen. Acetaminophen, like red dye number 40, is also FDA approved and taken by many people under the brand name Tylenol. Yet a cat fed acetaminophen will quickly die. In addition studies have found acetaminophen to be a cause of horrible liver damage in humans, liver damage that is also greatly increased when the drug is combined with alcohol consumption. Alcohol makes acetaminophen more toxic while depleting another substance that protects against liver damage. Despite this fact consumers are not properly warned. As Doctor William Lee has stated of victims of acetaminophen liver failure, “They don't know they've done anything wrong until they have nausea, vomiting and jaundice�.

A good example of a substance that is harmless to humans, but deadly to hummingbirds is honey. Honey water in a feeder causes fungal infections that kill hummingbirds.

Yet there is solid evidence that the FDA approved red dye number 40 is also probably harmful to humans. Mice fed small amounts of the coal-based food additive have been shown to have cancerous damage done to their DNA (Tsuda S, Murakami M, Matsusaka N, Kano K, Taniguchi K, Sasaki YF: Toxicol Sci. 2001 May;61(1):92-9). Rats have been shown to exhibit evidence of physical and mental toxicity from the dye (Vorhees CV, Butcher RE, Brunner RL, Wootten V, Sobotka TJ: Toxicology. 1983;28(3):207-17). While being a legal food additive in the United States, red dye number 40 is banned in Denmark, Belgium, France, Germany, Switzerland, Sweden, Austria and Norway.

Red dye number 40 is very likely to be harmful to hummingbirds and it is also completely useless. The only reasonable purpose of any red dye would be to attract the attention of hummingbirds (because they are attracted to red). Yet regular sugar water (one fourth sugar, three fourths water) is much cheaper than hummingbird mixtures and works just as good at attracting hummingbirds (as you can see at my feeder in the included photo). The red on the feeder is sufficient to bring the hummingbirds around and studies have shown that hummingbirds prefer the taste of the clear liquid when given a choice. To catch the eyes of more hummingbirds a red ribbon around the feeder can also be used as well as planting flowers that attract hummingbirds.

A good native plant for this area that has flowers that attract hummingbirds is Mimulus aurantiacus (Sticky Monkey-Flower). I’ve planted these in my yard and the hummingbirds visit them regularly for nectar. In addition, the Sticky Monkey-Flower also attracts a couple butterflies whose larvae eat their leaves, the Chalcedon Checker-Spot and the Buckeye Butterfly.

When it comes to the health of hummingbirds and people it is best to error on the side of caution. Yet the FDA, when dealing with human lives prefers to error on the side of capitalist profit. Many food colorings are toxic and as a general rule it is a good idea to avoid all of them.