what thread is this?

[BBdesigner]

Hi beading friends! I'm looking for this thread - do you know what it is? I thought I read it was silk but I think it is not. I can't find anything in these colors on this yellow hazard looking spool. any ideas?

 

[Pearl Dreams]

I've never seen spools that are that bright yellow color and cant seem to find them online, either.

 

[CortezPearls]

I am not sure...but looks like regular thread to me...by this I mean non-Jewelry thread.