Orionis is a low-to-medium contrast theme. Its most prevalent colours are magenta, violet, blue, cyan, and green.
The theme comes in standalone light and dark variants (see further info below).
orionis-syntax in Settings > Install > Themes. Or install it directly using the command:
apm install orionis-syntax
Project page: https://protesilaos.com/orionis
Orionis dark version: https://atom.io/themes/orionis-dark-syntax
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.