"Little Green men and Little Grey Men" Topic

Setting up a universe for both a RPG campaign and tabletop battles (probably using Xeno Rampant)
The little Green Men are pretty nasty kidnappers.
I was about to start painting my Greys but what should their relationship be with the Greens?
A) Originally, I intended them to have a dominate Merchant culture. Trade with anyone.
B) However, They look fairly similar to the Greens and so may have a distant genetic background.
Could this result in a being sworn enemies or very friendly and cooperative?
Interested in your opinions.

A couple of thoughts

The Greys are the original race and the Greens are a violent off-shoot; the Greys are the rulers and technical experts, the Greens do the wet work

The Greys are as suggested a related merchant class

The Greys and Greens are offshoots of the same race but have radically different approaches to how to work with other species – they have a distant and often unfriendly relationship

Just a few thoughts

Alternate dichotomies in SF which could suggest different approaches to consider:
Vulcans v. Romulans (Two rigid societies with divergent ideals and approaches)
Romulans v. Klingons (Two militaristic societies with extremely opposed yet sometimes almost equal views, goals and methods)
Ferengi v. Humans (I selected this as the Ferengi and Humans are more alike at their core than any other Star Trek cultures.)
Founders v. Jem'hadar v. Vorta (Not oppositional, but different strata and methods/approaches.)
Tok'Ra v. Goa'uld
Asgard v. Nox (SG-1. Note that they're not adversaries. One is just active and willing to interfere, the other are passive and pacifist, and will rarely intervene)
And don't forget the Aschen of SG-1: Appearing beneficial, yet actually the most dangerous and insidious of foes because they conquer by appearing to aid.

The latter could be an interesting approach if you're going for a campaign.
The Greys appear to be neutral and benign, and will indeed trade with others in the galaxy… but they're really just gaining a foothold and creating dependencies in their target cultures/worlds which will place the Greys in complete control… or even reduce the target race to extinction.
The Greens are violent and aggressive, but really they are testing the resolve, abilities and defenses of potential allies against the Greys! The Greens do not accept words or superficialities— they seek concrete, perceivable proof.
(Now, that's a TWIST!)

I see the Greys as the nasty kidnappers (going by the Abduction lore out there.) The Greens, otoh, are more likely to invade, or try to take over your planet through more subtle plans… ;-)

Thanks for all your ideas!
I will go with the "distant and unfriendly" relationship.
But with the underlining possibility that the Greys are actively and deceptively "creating dependencies".
Wow that creates an interesting potential future story plot.
I just got back from basing my first ones.