The idea is that it will reduce animal suffering, but it's more complicated than that.
Shoppers in the United Kingdom have been urged to buy white, not brown, eggs from the supermarket. According to the Department for Environment, Food and Rural Affairs, white eggs are laid by hens that are less aggressive, which means that, should demand go up for white eggs, farmers would not need to trim beaks as often.
Hens that lay brown eggs, on the other hand, typically have the tips of their beaks cut off using an infrared laser when they are just a few days old, a process believed to be painful. This is done because the hens "have been known to peck each other to death to establish their hierarchy and are even prone to cannibalism." If their beaks are trimmed, they do less harm.The recommendation has ruffled some feathers. Critics point out that the hens' aggression may have less to do with their breed and more with the fact that they are typically kept in cruelly cramped conditions that lead them to behave in those ways. Or, as the Guardian put it,
"It feels a tiny bit as though farmers are repackaging their cruel beak-ectomies as the consumer’s responsibility. It also, at the risk of being overemotional, sounds as though aggressiveness may not be innate to the brown-egg layers. It could just be the conditions they have to live in, on a busy production line, that may make them aggressive to the point of homicide and (apparently) cannibalism."
Brown eggs became popular in the UK in 1970s when people began perceiving them as healthier, rustic, and closer to the land than white eggs. Currently, 11 billion brown eggs are produced annually in the UK, compared to only 45 million white; meanwhile in the US, white eggs dominate the market. This distorted perception of health "coincided almost exactly with the concept of brown bread as the health-food option, which was true, the Chorleywood process of speeding up fermentation and overprocessing white bread having been invented in 1965" (via the Guardian). When it comes to eggs, however, it is inaccurate; brown and white are nutritionally identical.
But if we're serious about health, we should not be buying eggs from a supermarket. Eggs from free-range chickens have "two-thirds more vitamin A, double the omega-3s, 3x more vitamin E, 4x more vitamin D, and 7x more beta-carotene" than factory-farmed eggs. It's a kinder existence for the birds, too, who live in smaller flocks, with greater space, and can forage naturally for insects using their sharp beaks.
This debate creates a good opportunity to think about where our eggs come from and how to source them more ethically. Look for local farmers or food co-ops that sell free-range eggs. Consider cutting down on egg consumption to reduce demand (although from a climate perspective, it's a far better form of protein than meat, fish, or cheese). You could even look into keeping a few layers in your own backyard; I've done it and enjoyed it, although you should know what you're getting into. Just don't buy the whole argument that switching colors is somehow going to make industrially caged birds' lives easier. It's bad no matter how you look at it.