If you intend to do this with heat? and it's just putting the finish on a steel case that you have in mind, it can be done in theory, although I've never seen it done on a PC case before
Just for a bit of background (the engineer in me can't help it): The blue patina is actually a color that you get when you're annealing steel, a process to make it softer and more ductile. It's the opposite to case hardening where you heat steel to cherry red in contact with carbon, aiming to increase the carbon content of the outer layer to increase it's hardness/reduce ductility, case hardening usually leaves you with an uneven black patina, like something fresh out a forge
If you do want to try it, there are two ways of getting the blue patina, both will only work on steel, and you would have to be able to remove all the hardware and plastic parts from the case first:
The first is with heat and would allow you to get a deliberately uneven patina where the color fades into the original color of the metal (like on the RAM you mention), to do this you would have to strip all the paint off first to avoid poisonous fumes and burnt paint spoiling your finish, then you would probably want to polish or brush the steel because a patina won't change the surface texture of the metal.
A blow torch would be the easiest and cleanest way to go, I would heat the metal from the inside so the soot and black isn't seen, the blue will form just before the metal starts to glow dull red, and don't let that happen because as soon as it does the steel will warp out of shape, go easy on the heat and do it in low light so you can see sooner when the metal starts to glow. Also, practice on some scrap sheet steel of a similar thickness first because getting the effect you're looking for without overheating and warping the plate will be tricky
The second method, the one used for guns, is a chemical patina, I've used a product called "Perma Blue" made by Birchwood Casey in the past. With this you don't need heat, but you might have difficulty getting an even color over something as big and flat as a PC case, and you won't be able to get the fade in fade out effect that you can get with heat, I'd recommend watching YouTube tutorials on how to blue guns to give you an idea on how this works, and again, practice first
If you try it, let me know how it goes, I'm interested 😉
and as for the corsair RAM, the color there is likely to be some kind of plastic film coating or print just to replicate the effect, because it would be very hard to do reliably and repeatably on a production line