Faithful... but only just
Manservant was a playable character in the Camelot Game. ("Stoke Me a Clipper")
When Lister needed to do something about his sexual frustrations, he used an AR game featuring himself as a knight who seduces the Queen of Camelot. In order to do this successfully, he needed Kryten to join him in the program as his faithful manservant. Kryten was unhappy in this role, as Lister was using cheats and underhand tactics to act in a very unchivalrous way.
The Manservant was unnamed, but dressed in the livery of his master, which included a dark blue robe and a flowing hat. Kryten held Lister's cheat book while he killed the Good Knight and took the Queen to his tent. Kryten reluctantly assisted Lister, but still described him as "Scum".
The program ended prematurely, when Ace Rimmer's ship disrupted Starbug's systems. ("Stoke Me a Clipper")