The title says it all. I have these emperor puffs I want to sell offspring for, but all my attempts have failed. Advice?

I think most people are only interested in buying themed pets (fabled ones like Nephini or Ferrikki are usually more popular than non fabled ones), especially if they're 6 vis and max statted nowadays. Some people probably would still buy normal 6vis if they find the color combinations are beautiful. Btw, I'm not that good in selling pets as well so I could be wrong here.

I'll agree with Luga that themed offspring and themed pets are in demand, especially now that their are purebred tags. Project pets might still sell though~ it really comes down to finding people who like the theme and who'll buy offspring. Color combinations, species and trait combos as well as stats all affect the possibility of sales.

For an example:

Duke and Duchess are my legendary Zolnixi pair.



I can consistently sell their offspring for 40k gold, super easy. None of their offspring ever make it to adulthood in my stables. They sell before then. xD
Zolnixi is a popular species and this set has some popular traits, the color combination also tends to sell well. Another user borrowed one of my designs from the Puffadore Revamp that shared this color palette (The name is Calicute, you can find them via advanced search) and they also sold well.

Then we take a look at Specter and Asteria.



The color combination is fine and a lot of players have complimented the paladin draeyl~ however the species is still a Draeyl, which is one of the most unpopular species on Sylestia. Specter has great traits, but Asteria's are less desired. If I could get spitting images of Specter from their offspring all the time, they'd easily sell from 30k-40k. The other babes have unfortunately sat in my stables from 20k-25k and haven't moved. xD

Species. Traits. Color Combinations. Stats.
Those are the four things to remember when working with project pets.
(Also, pretty sure a lot of Sylestian's are partial to the color blue. xD Red/orange are fairly unpopular.)