I've also used 'monofilament' fishing line before now.
It's near transparent, available in different gauges (strengths) and does have a bit of 'give' if that's what you want.
If roving through blocks /pulleys etc I put a small blob of 2-pack epoxy on the end to stop it running back through….also, you can "double-it-back" through some electrical sleeving to form a loop for securing to a bollard, cleat etc
I think it may take paint as well, but I haven't tried this. Most fishing shops will have some on a round reel for a few pounds.
Dave