As the title says, after you've decided upon a style and color for your monk's ki the effect does not persist through server transition or reset. You can only choose it once, even after it's disappeared, the command does not allow you to choose again to reapply the effect.
The only workaround right now is to relevel through the -relevel command, level back up to your 20th monk level to gain another use of the -ki_color command. Not the best of workaround and it's likely to raise a few brows when viewed in the log since you have to do it for every server, every reset.
Maybe a command can be implemented to reapply the choice as a temporary band-aid?