The colour determines its wear from the rods that are either rotating or traveling up and down.

There is blue,yellow,green and red paint aplied to the pipe when removed from the well.
Blue,yellow and green are ok for service still.
Red is not. Red can be from to thin for service to hole in side( really a crack from the pressure)
Or it's pitted from corrosion.
Any red band( red paint band) pipe that is still strong is sold to welding shops.
That's where I got mine from.
I cannot say how ductile it is cause I'm not a professional welder or fabricator and haven't compared it to Dom or chromoly exept for price.
I got mine for 50 cents a foot.

 

I did a brief internet search and found several discussions on different boards of using schedule 40 pipe vs DOM tubing for roll bars / cages. Considering my sources I'm sure the information is completely reliable

With that intro, what I found is that some people say never ever use pipe while others say it can be as good or in some applications even better.

The downsides of pipe seem to be:

• brittle so it cracks when hit hard enough, possibly even creating shrapnel
• if galvanized it doesn't weld well (solution to this is to use black gas pipe rather than galvanized water pipe)
• heavier per foot due to thicker wall

The upsides to pipe seem to be:

• cheaper
• stronger due to thicker wall (but not universally agreed upon)
• more wear resistant so it holds up better as a rock slider (makes sense to me if it's more brittle, that usually means it's harder)
• doesn't dent when hit (again makes sense if it's more brittle, it won't deform when hit until it's hit hard enough to break it)

So maybe it's not so cut-and-dried that pipe isn't acceptable for roll bars / cages. Personally I still think I'd stay away from it, but apparently there are quite a few cages out there that have worked well for people.

 

I'm wanting a roll bar

 

Just so you know, a "roll bar" has ZERO roll over protection. It is for looks ONLY

 

Pipe is banned by every respectable race and offroad organization in the world. It was used in the past with horrific results, which is why it's now banned. Even the cheapjack LeMons beater racing series and the demolition derby outfits ban it. Mostly it shatters on rollover impact *before* the vehicle comes to rest, which on our trucks (and trucks in general) means that it's going to flattop with you inside.

There are offroad parks out there that *will* bar you from entry with a pipe rollbar.