According to an Eventbrite post, Nickelodeon Casting plans to hold an open casting call to find the new host for Blue's Clues on April 14, 2018 in Burbank, California.
The post says that Nickelodeon is looking for females and males of all ethnicities, "who can play 18-25 years old."
People who want to audition need to be at least 18-years-old.
Nickelodeon wants their host to have a background in comedy, be naturally connected to the camera and be able to "empower the home viewer to feel important, respected and smart."
Unfortunately, if you are looking to audition, all the time slots are filled. So there are no more spaces available to audition.