Do not breed it to a tricolor. Tricolors are really hard to work with if you want showable colors - not only are their solid version (harlequin) not showable, but rabbits that carry tricolor often get harlequin stripes or spots that make them unshowable. That would be the most likely result from that mix - harlequinized chestnuts or harlequinized otters.
Otters and tricolors are two very different color projects, both which are much more restrictive in crossing than most colors in holland lops. Both of them are generally low quality in holland lops compared to the more common colors (tort, etc) - there are good ones out there (I remember judging some gorgeous black otter hollands recently, but I haven't seen a good chocolate otter yet) but they are much fewer and far between than good torts. Honestly I can't think of a reason to cross those two, and it would likely not improve the type of either of them. Be careful when buying interestingly colored hollands like chocolate otter - make sure the breeder factors in health, structure and temperature and not just color.
One of the difficulties of otters in holland lops is how common tort is in the breed... your best bet for getting good type on offspring is breeding to a good tort but that is likely to throw torted otter babies which are not showable. If you would rather settle for a higher likelihood of showable colors and maybe not as good of type a black, otter or chestnut (or a broken version of those) would be your best bets for a cross.