I like the idea of beings composed of light and music. The various colors and musical notes that represented their personal qualities were a different approach to creating alien characters. Yet as a librarian, the strings of numbers separated by decimal points that were part of each individual's designation, reminded me of Dewey Decimal classification. I kept on wondering if I should be shelving the Chroma.
The need to participate in the lives of mortal finite physical life forms is understandable. Limitation makes existence more intense. The unending life of the Chroma lacked purpose. So they found their sense of purpose by observation of physical species at first. The Chroma entity nicknamed B4 seemed to become emotionally involved in the lives of individuals. There are some very lyrical descriptions of B4's experiences and perceptions.
Eventually, they started feeling as if Earth was their laboratory, and that anything was justifiable if it could be considered an improvement. I lost sympathy for the Chroma when I realized that the needs of individuals weren't a priority for them. Even B4 seemed to have lost sight of the importance of particular beings in the species that were the subjects of experimentation. This is probably a consequence of the Chroma belief that sharing consciousness as a group is paramount. Their super-human immortality also gave them an impossibly long range perspective. They thought on the scale of evolution.
It seems to me that evil lies in extremes. Forgetting community and focusing solely on your own needs is one type of evil, but focusing solely on the group whether it's a community, a country or a species also often leads to terrible consequences despite the best of intentions.
I feel that there should be a balance between the needs of the group, and the needs of the individual. Maintaining that balancing act is challenging, but this doesn't absolve beings whether they are human or non-human from the responsibility of attempting to achieve that balance. Scientific experimentation also needs to be done responsibly. That is the conclusion that I took away from my reading of this novel. Other readers may feel differently. I wanted the Chroma to have a wiser and more complex understanding of the consequences of their actions.