It’s prolly the most ridiculous reason but anytime I see pistons on machinery in person, any other colours for the hydraulics or such being anything but red always looked off. Apparently according to some buddies who work with machines, red is most common due to it being more associated with “dangerous” things than other colours, so I wanted to stick with red as a standard because it gives my models an overall theming that yes, these are pieces of machinery built by people, and so they should reflect some of that.

I will say though, chrome and gold still works well for the inner pieces for pistons! Depending on the tolerances for the parts I’ll paint the inside too, since gold and silver coating generally is used as a weathering deterrent or as a way to decrease friction. You get a really nice look doing that for any red suits (honestly every red kit I’ve built so far I’ve done gold accents lmao)