I think "Chess.com Standard Theme" is the original theme. It's on the very top of the list.
Original theme

It's not.
Try to apply it and check your profile page. Then go to www.chess.com page and you will see the differnece.

Yeah, your theme looks different on my computer as well. But my theme doesn't look like yours (at least for me). I just switched back to the original one by changing to the "Chess.com Standard Theme," and I can't see a difference between it and the original. Does my page look like your page or the chess.com home page on your computer?
By the way, did you actually click on "use" or just "preview"? They have a bug such that when you're on preview, it doesn't always change the backround from what your current one is and only changes after you click "use."
Hi,
I wanted to try different style themes. I went to account settings and applied different themes but later decided to go back to the original one, the one you can see on chess.com main page.
Unfortunatelly, I cannot go back to the original theme anymore!
Once I select "Classic Chess.com" from the list of themes, I have a similar theme but it's not the original, it doesn't have the dark gradient on the background and it has white background in the top and in the bottom parts of the website.
How can I get back to the original theme?
Regards,
SM777