Either:

1. Discord (https://octarine.app/discord)

2. Github (http://octarine.app/issues)

Currently the app supports 33 themes (3 free, 30 on the pro license). There's an item on the roadmap that would allow you to create your own themes (each theme is a palette of 10-12 variables - border/bg/text/outline)

Hope you like the app :)