Ouray base in sector C6 of the Colorado system is a Xeno base. You can use trade lanes to get very close, and then explore that sector, checking your navmap every once in a while to see if you've detected it.

The difficult we do immediately; the impossible just takes longer.

There's two that I know of:

First is Ouray base in Colorado, around C-6. The second is Nome Base, in Kepler. It's around the intersection of C-5 and B-6.

Ouray base is much simpler. The Xenos around there are generally rookies in Startrackers, whereas the Xenos around Nome are Ace pilots flying decently-equipped Hawks.

Thanks alot Nightsilver and WarPig, thats exactly the king of information I needed.

There are three bases that belong to the Xenos as far as I know

The already mentioned Ouray Base in Colorado
It's more or less on the line between C6 and D6, so right in the center of the two

Also mentioned; The Nome Base in Kepler
It's in sector C6 in the northwestern part of the sector

And the Barrow Base in Hudson
That one is located in E3: southeast of the sector