Sorry, I've been packed with work recently so I didn't respond earlier.
While looking at an ingame version will certainly not hurt, I'm pretty sure I can already tell the color needs some adjustments. In short, your colors have a noticable Blizzard-esque/cartoonish look. We're going for something more organic, with less saturation and more slimy reflections.
Let me show you a few examples of our current aliens.
The acid tube was among our first complete alien structures and thus was setting a standard for their appearance. This doesn't mean we want other structures to copy its exact colors but the general notion of organic material is still a good reference:
Here are the texture maps for the acid tube.
You could also have a look at some of the mobile alien forms, for example the Tyrant:
Or the Dretch:
You'll notice that our main colors are tones of brown, red and teal. New colors are certainly welcome but the result should still roughly fit into the alien family.
For the Spiker, maybe given the flesh a very dark tone (like the Tyrant skin) but make the "shell" a slimy, skin-like surface similiar to that of a ray?