I usually split Textual and Telegram client in full screen side by side. And Telegram has a pretty awesome Night blue theme I use and like.
I changed TotalSublime theme colours to match the Night Blue look of Telegram.
Here is how it looks side by side:
To install the theme, download the Night Blue folder attached here.
Then go to Textual app. Go to preferences and in Styles click on Browse Styles here:
Put the downloaded folder inside the folder. You can read this for more information.