Other examples of Stubhub e-mails include "fieldmilestone" and "rolodexinfo". I believe that Stubhub is using old domains, probably from some list that their registrar is providing them. Sometimes, there are blocks of patterns, such as the color/etc. one - but they're probably doing this to avoid getting spam-filtered by people's mail clients, not to try to hide from Ticketmaster or anything else, and I doubt the naming is something they are defining.

All the ones I've seen are quite recent, 2023 creation dates. Your "fieldmilestone" is one such.

Obviously they're not literally all the color+feature+company pattern but I don't think they're just reusing old "real" domains either.

As for not getting spam filtered, using a big pile of new domains with no web presence probably has the reverse effect so I don't think that's the intention here. Also I think as it's described, these emails aren't really sending messages to people, they're there to receive emails from Ticketmaster or similar entities when you go to transfer though them.