So it looks like there wasn't any discussion here about this yet, or at least, not any complete discussion, so let's talk about element and its many colors and forms.
What we know as a fact that element can exist as:
-Solid metal (Aberration boss terminal, tek cave, element we use)
-Gas (lunar biome)
-Liquid (Aberration, tek cave)
-Crystal (Aberration Diana #18 "crystallized element shards")
-Whatever the purple glow of Corruption should be called
So we know for a fact of the existence of 5 different forms of element.
This next part took me a while to get a decent hold on, despite being mildly implied since the Island, I only realized the evidence after Extinction.
The different colors of element:
-Green
-Blue
-Red
-Purple
I don't think it's necessary for me to provide proof for that part, everyone's seen these.
Now, ever since the Island, it was implied that there was a sort of hierarchy between red, green, and blue from the boss difficulties and ascension implant colors, but there was never any proof. In Aberration, we have green gems, blue gems, red gems, and purple gems, along with the existence of purple element now.
The furthest gems from the core of Aberration are green. If you go closer to the core, you find blue ones. Go further and you'll find red. Keep going and you'll find purple gems which turn red as you gather them. Diana's note #18 tells us that element can exist as a crystal (gem) and we see the color hierarchy we saw on the Island too in the gems. Later, in Extinction, we find blue and red crystallized sap that is functionally the same as the blue and red gems. This makes sense if there's actually blue and red crystallized element there, which would also make sense due to how much element is on Earth at the time.
Conclusion: The green, blue, red, and purple gems are all element.
To ignore the color hierarchy at this point would just be silly. It's clear that Wildcard has been pushing the whole deal with different types of element a lot (without going into theories, we already have 5 different types,) so we can say with confidence that the different colors of element have their different meanings.
The power hierarchy of element goes as so: Green < Blue < Red < Purple
This breaks the earlier assumption that purple element = bad and blue element = good. That thought worked well enough going into Extinction, but it wasn't completely correct. The purple element is dangerous because of its high energy levels and radiation in its liquid form; it's also the color used by Corruption (why would Corruption want to use a weaker form of element?) Blue element was only considered to be good because it's the easiest to make use of (which does, still, for all intents and purposes, make it the best color of element for us.)
This has some further implications about our good friends: The obelisks.
On every Ark (Aberration not included) there is one green, one blue, and one red obelisk. This means that there is one low power, one medium power, and one high power obelisk. What exactly is the purpose of this? I have no hard evidence for anything about this, but I guess it works like a reservoir system, with anything that needs more power being able to pull from the red obelisk if needed, and anything with too much energy could dump into the green obelisk, while the blue obelisk serves as a backup for both (if the red one is getting too drained, they can pull from blue, and if green gets too full, they can dump into blue.)
Also, I have a feeling that congealed gas balls are also some sort of element, but I have absolutely no proof or reason to believe this.