Under the show coordinates bar, invisible zombie with wither skeleton skull turns green and yellow, and not shown in the video, it will turn red and blue every so often. 

Because of the file max, I put a video here:

https://cdn.glitch.com/b27968b6-063d-4ad8-aa6e-094d527a9c0d%2Ftrim.70A342B2-AA73-42EA-A55E-446EAAB1B00A.MOV?v=1591242307345