Maven Central versions with a red background

I was updating my version of the javassist library and noticed the latest version (3.22.0-CR1) on the maven repository site has a red background, but with a quick search i wasn't able to find out the reason for that.

Can anyone please explain what does that red background mean? enter image description here

What are the three types of Maven repository?

There are 3 types of maven repository: Local Repository. Central Repository. Remote Repository.

What are versions in Maven?

1 Version Numbers in Maven Coordinates. The version number of the artifact defined in the POM file is the same as the version number of the released product, for example 12.1. 2.0.

How many types of Maven repositories are there?

A repository in Maven holds build artifacts and dependencies of varying types. There are exactly two types of repositories: local and remote: the local repository is a directory on the computer where Maven runs. It caches remote downloads and contains temporary build artifacts that you have not yet released.

Because it is a pre-release version (it isn't a stable version).

https://github.com/jboss-javassist/javassist/releases/tag/rel_3_22_0_cr1

enter image description here