Anything that has a coating, will wear quickly in Pinball machine. The balls often get a very high spin on them, then smash or scrape into metal surfaces... such as ball rails, and often hit non protected edges... ball hops and such.
To make a ceramic, I believe they use a powder format, and mold & heat it. By adding the UV pigment in the mixture, it would be blended into the entire ball, rather than the mere surface... thus any scratches and damages, wouldnt look atrocious.
The problem is that Ceramic balls are much lighter than steel.. and so they would not react the same. The gameplay would be a lot faster, and less controlable. Twilight Zone is a fairly slow game.. so the extra speed of the powerball, isnt so bad.
Not sure if you can properly center a steel core inside of ceramic material... but that might be another option.
Other ideas...
An x-ray machineing cnc device
2 part Ceramic half blocks partially fired, ball inserted & all bonded with additional Ceramic, fired completely.
CNC device that can print the Ceramic on a steel ball... and or a cnc that can print both steel & ceramic layers...
Thin Steel string hung ball (or maybe carbon fiber string?), centered in ceramic block mold
Magnetically centered ball in chamber of ceramic mold
A mixture of metal powder and plastic / urethane / and or ceramic.. to create a hybrid ball with low friction, colorable, and high density
Chose another material altogether... with the same density, but is much more friendly to coloring in its mixture.
Im not a materials expert.. but Im sure someone in the field could figure it out. The expense of them however, might be beyond what many would choose to pay. Ya never know though. Pinball is getting to be a rich mans hobby, as machine prices jump in value yearly.