No real official guides as far as I know, but most of it is up to the subjective whims of the buyer. Rarity of color combo doesn't really mean anything on its own (and without a wolf search is hard to determine anyway) if those colors don't appeal to someone out there. :P
There are certain trends, natural colors are popular, so are pastels and black/neon or eyeburners to the right folks.
Flea market trends can show you what wolves of a similar range are being listed for, tho not so much if they actually sell for that.
A lot of very cute pups go for relatively cheap, 'cuz LW has considerably more dogs for sale than there are active players with den room left to take them in-- there is a current cap of 50 slots per den unlocked, a cap of ten dens, for 500 wolves per player total (which sounds like a lot, but we are well into 350,000 total wolves born already). That doesn't mean you need to start at rock bottom though, it just means don't get discouraged! It might take longer for a pup to sell and you may need to adjust the price a few times.
Generally, you don't want to list anything for less than 1000kp, 'cuz 1000kp is what you get for releasing a level 1 wolf of any age, so those will be snatched up for however little profit they are worth to release. 10,000kp (and a KB token) is what you get for leveling and releasing a level 10 wolf, so if you want to avoid your pups getting passively leveled by people using basidos for release profit, it might pay to price them above that. I think most people breed their own fodder right now, but it pays to keep in mind I guess?
