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I think genderless pets are awesome, but if you don't like it, you can always zap the pet until it gets a gender. Just know, you can't make the pet genderless again.
I heard if you use a (quite expensive) Sex Berry to a genderless Pet it'll be given a random gender, however I never tried that so don't count on that 100%. Same should be possible with the zapper, that's why most people don't zap their genderless Pets if they want them to stay like that. Personally I'd be happy to have a genderless Pet. pokes Khaos Too bad there isn't an option to change from gender to genderless. ^^;;
Wow, how did people get genderless pets? I'd say zap him if you want to give the pet a gender, and you can always turn the pet back to an arid kumos. The Arid Kumos Elixir is not very expensive.

Your only option is to adopt an Endeavor or Cadogre when they are available on Atebus ~ it's a rare event though; at the moment however there are quite a lot genderless Pets in AdoptRUs. C:
If you want to create a genderless pet, go to Atebus' Adoption Agency when there are either Endeavors or Cadogres available. There are some now.
I was going to suggest a sex berry for keeping the color and changing the gender, but they're kind of expensive (3m) and I have no idea if it would work with a genderless pet. Sorry.
As for keeping the color, try and Arid Kumos elixir or one of other colors/species. Most aren't very expensive. Or you could keep zapping and maybe get an awesome color change as well.