How do I get my Tumblr dashboard back to normal?

Okay, so, I was using Tumblr, and I saw other people had different themes for their dashboards. I thought it was cool, so I decided to get one myself. I had to install a program called Stylish (I use Google Chrome). I tested a pink floral theme for Tumblr and liked it, so I kept it. I got tired of it and wanted to change it. So I went to install a new theme, but once I did, it wouldn't replace the pink theme. I waited a while and refreshed the page, and the new theme popped up for a second, but then the other theme came back. I got frustrated and researched, and found nothing. I clicked "uninstall" on the Stylish icon in the toolbar, but that didn't do anything. I clicked into "installed themes" and that theme I downloaded wasn't even listed. How can I changed my Tumblr dashboard theme back to normal? This is very bothering!