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Xenomorph is race from films Alien (1979), Aliens (1986), Alien3 (1986) and Alien Resurrection (1997).
We can find them in AVP: Alien vs. Predator (2004) and AVPR: Aliens vs Predator - Requiem (2007).
Xenomorphs are also connected to films Prometheus (2012) and Alien: Covenant (2017).

As a source for most complete information, I recommend looking at Alien Anthology Wiki and Xenopedia.

Main decision in this costume is head - flat (smooth) or bumpy head?
The difference is often considered to be two castes - Drones and Warriors / Soldiers. But as you can read in Warrior's Trivia: James Cameron stated in the Aliens commentary that Warriors are indeed the adult form of the Alien. You can also look into Drone's Trivia: Actual Drones were originally going to appear in Aliens but during pre-production the creature's smooth carapace was removed out of fear the fragile dome would crack during filming, a modification that gave rise to the Warrior caste.
That is all nice but for what did I decide? I did not - they are both same except their heads (at least as far as I can say) so there is no problem with having two heads and one body (until I want to share one to someone else).

When looking around Alien Anthology Wiki, you may possibly find Red Xenomorph from Aliens: Genocide (comic).
In short, Red Xenomorphs are different race / breed and in war with Black Xenomorphs because they are not pure.
I was thinking - what if there was no war? Yes, that is not in their nature but is in reach of our imagination.
I took Black Xenomorph as base color and added red details (in my mind). That created my own (color) version of a Xenomorph.