Telegram for Android receives custom theme support and theme editor in latest update1
The update comes with three themes pre-installed — the default one, a blue one, and a cool new dark look that's perfect for texting late at night — but you're probably going to head to the new built-in editor and make your own one anyway, so that's that. The editor itself is nothing overly involved, but allows you enough freedom to fine-tune the various colors across Telegram's UI to your liking using a color wheel.
If you don't feel like creating your own theme, but would instead like to check out what other people have come up with, you can head over to the @Themes channel for some user-created looks for the Android and Desktop versions of Telegram.
According to a blog post by the company, iOS users won't be left behind and will be getting not only custom themes in the near future, but “something different” and “truly epic” as well. They will just have to “hold on for a couple of weeks”.