Custom colors and themes
I have literally been using Yahoo Mail for maybe 25 years, or perhaps even longer. And with just one move, you have stripped all the soul out of my inbox. I hate this soulless, plain white or black page. Why did you do this? You have all the resources to keep both versions available. I'm truly on the verge of losing all hope in Yahoo. Honestly. I don't complain any of the notification clutter of your website but... You shouldnt force your long-term, loyal users into this.
Thank you for your feedback! We know our reply won't make you happy, but unfortunately there is no reverting back. Very sorry. We are EOLing the old version and only making the new one better. We decided to simplify our themes because more than 90% of our users kept the default, therefore with very low usage we decided not to support more themes and backgrounds. Thanks!