Semantic highlighting for almost any language in Atom. Colors are used to highlight the important parts of your program: the variables, methods, and classes.
For more about semantic highlighting, see the article Coding in Color by Evan Brooks.
By default, semanticolor also accentuates comments to make them stand out. This option can be turned off in the settings, but for the reasoning behind it, read Your syntax highlighter is wrong by James Fisher.
These are the meanings of the available language options:
Base 16 Tomorrow Light
Base 16 Tomorrow Dark
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.