[digger48]

I figured it would be red steel, like most I beams are in building frames

Looks like it’s not painted at all, so it needs paint of some sort

[redshawk]

coreten steel is what is being used.
https://en.wikipedia.org/wiki/Weathering_steel

[cymbeline]

“Looks like it’s not painted at all, so it needs paint of some sort”

Yes the steel needs a paint cover. Might as well be black.

But if they do their climbing at night ...