Bwahahah, yes it do be like that. 40k is 100% over the top and it also takes itself 100% seriously. Imagine if Michael Bay and Tommy Wiseau made a universe together

Ok I'm still learning but here's is the lore I know they where engineered this way by another powerful race called the old ones. They were meant to battle the Necron and their gods so they created them as violent self sufficient fungus that spread though spores. The way they access tech is by using a pseudo low level psychic field that trends to accumulate the more orks are involved, as long as others believe in the same thing working. Going to the red paint many orks seen red things go fast so the started believing that the characteristic of being red is what makes them fast. When enough of them do the psychic field nudges reality to make it work. But the trick is first they are not aware of the psychic thing at all we know it as readers but not much more. Even the other races barely know what's the deal with them, we humans have stolen artifacts from them and they stopped working on our hands. And the other factor is they have a low level creativity and intelligence; everything they believe It gotta start somehwere so logic apllies to the ones who started or is something it has been observed by many, like how they make their version of titans they just saw a big robot and they wanted one.
There's a final factor which makes all this understandably harder to get. Warhammer is a franchise that has been aroung since 1983 with many writers involved in its lore, making parts of it a decade spanning broken phone.

Green is best because Orks are green. Yellow means more which translates to bigger explosions or wealth. Blue is lucky. Purple is sneaky. White is extra killy, usually used for melee weapons. Black is tougher.

I think red is the only colour they believe has an my significance. You’d have to ask an Ork to be sure.