Using a fresh install of maven 3.3.9 I followed the steps at https://garygregory.wordpress.com/2015/03/23/watch-maven-in-color to add color highlighting to my output. Everything works as expected, however on all usages I would get the warning:
This looks pretty harmless, and I was able to suppress it by manually adding the line
to /META-INF/maven/slf4j-configuration.properties in maven-embedder-3.3.9.jar.
I'm not sure that this is a "correct" solution, and I'm not even confident I could explain what effect it has, hence not posting a patch, but somebody with more knowledge might be able to triage this better. Or offer an "official" way to do colorized output.