Except your fork now prominently appears even after the PR is merged. However, I don't think Github has a way to see all your PRs.
https://github.com/search?q=is:pr+author:YOURNAME&type=Issue...
Here's how to see all your open PRs:
https://github.com/search?q=is:pr+is:open+author:YOURNAME&ty...
Replace YOURNAME with your GitHub handle, or pick your colleagues names.