- I had a comment for you, but it is too long for comment... so I made it longer.
- I also noticed that my latest draft did not save and some of the points and quotes I had are missing... I will try to remember to add them later.
- This is kind of becoming an answer and might point you in the right direction or give you some more insight
- Your answer about how their tech works and is red really faster is likely in an Ork codex or as an aside in a novel if it can be found anywhere.
- But Orks did develop the technology to travel the stars, by accident.
- They do have a latent psyche that at the very least attracts them to one another, especially when a certain faction is successful in battle.
As far as I know the Ork psyche has never really been explained. We do not know the full extent of their abilities or how it all works exactly. I only have all the released rulebooks, but nothing as far as codices for the Orks or any novels that feature them.
First I will mention a couple points that attempt to debunk the entire idea that the Ork psyche is an all powerful force that works only in the Orkish favor and is the key behind their technology working and the ideas that 'if an Ork believes it, then it is true.'
This page I found here sheds some light into how Ork technology did, albeit by accident, develop into their ability to travel the stars: https://i.warosu.org/data/tg/img/0460/26/1458029629654.jpg
This link is important because it shows that the Orks developed/discovered the technology to travel the stars and does mention that their force fields were the origination of keeping the space hulks they traveled on air tight and supporting atmospheres. In addition it also shows that they build things, not just imagine them into existence. (Though it could be said the latent abilities are what lead to the breakthroughs initially...)
Also in one of the Space Wolf novels (I believe it was from Ragnar's Claw by William King) Ragnar and his merry band were infiltrating an Ork detachment of some size and commandeered an Ork trak. So non-Orks were using Ork vehicles/technology without issue. It could be said that if an Ork or high enough number of Orks are not in the area that Ork tech will not function, but Space Marines were able to not only use it, but they also raced another Ork trak as well pushing it to the limit (I do not remember who won?!).
What I can tell you about the Ork psyche and other somewhat related details is this:
In contrast to the answer posted by @Yasskier I will also argue that the Eldar did not create the Orks. I could be wrong but this image I found has a quote from and Eldar about Orks being the pinnacle of creation: https://img.fireden.net/tg/image/1446/50/1446506377038.jpg
I believe that there is still a unified idea that the Orks were genetically bred, the only question is by whom; be it the Old Ones or otherwise, but I don't think that quote fits if they created the Eldar.
Orks are born of spores, hence the mushroom ideology. The rulebook that mentions this is the 5th Edition:
A numerous race, the Orks are never truly beaten, for when an Ork is finally killed he releases thousands of spores that settle in dank places and eventually mature into yet more Orks.
Second I can tell you that Orks actually grow in size after engaging in successful conflict/combat. I am still searching for which book mentions this, but I know it is there somewhere... I believe this is the primary way that the Orks grow in their stature. I would argue that this is connected to their psyche as well, possibly even that the Orks who witness the success feed the energies into the successful Ork for him to grow in size and power. Though if I don't find this quote I will be upset because it is basically the same as 'red go faster.'
Third, When Orks gather in large numbers they essentially create a homing beacon for more Orks, this from the 6th Edition:
Large conglomerations of Orks generate mental energies, their bloodlust echoing through the Warp to act as a beacon - summoning more greenskins to join their cause.
Though this is also dependent upon the Waaagh! continuously having success. Also from the 6th:
Success breeds further success, and every Ork victory calls yet more greenskins to join the cause.
This would mean that at a point of failure the Orks "beacon" would be turned off and Orks would no longer be drawn to the area. Therefore the collective psyche of the Orks is dependent upon success and their morale not being broken. I believe that it is possible, given that we have no true source as of yet regarding Ork technology, that this is where the ideas of "Orks think red is faster so it is" and "Orks think the behemoths they build are powerful and so they are" ideologies come from.
Though I also came across this trying to find some codex page screenshots on google:
Orks, having an understanding of the universe built into their genetic memory, obviously having an innate understanding of the doppler effect. Things moving faster away from the ork have their colours red-shifted, and hence an ork would recognise that fast things look red. Ergo, red wuns go fasta.
I'm not sure where they know this from, but it could be a purely scientific type answer to that thought process and unfortunately de-mystify them even more.
I believe that the closest rationale or explanation we have of how the Ork psyche works is from the 7th Edition:
The Ork psyche is so strong and robust that their reflection in the mirror-universe of the Warp is a potent force indeed.
And while this may enlighten more details on how their psyche works it is also the cause of more questions, primarily, why the 'mirror-universe' of the Warp and not just the Warp? So do the Orks have their own layer of the Warp carved out in a mirror-universe that their presence resides in?
Like I said, these details do not answer your question, but perhaps they shed some light on details you may not have known or another user may have their memory jogged of something they have seen that may shed some light as well. And of course a lot of these details are from older editions as well. As much as I hate accepting GW's reversals on published lore, some of these could be skewed or entirely reversed in the newer codices.