Enameled copper wire colors
 

I have a couple of coils I need to re-wind but I'm not sure what wire to use. It's often red or green and I have plenty from scrap sets. I don't know if the coating color denotes a critical difference, i.e. a difference in wire gauge that isn't readily noticeable or what. So, what's the 411 on this stuff?

What matters is the gauge (diameter), turns count, and sometimes that the wrap style be the same. AFAIK the color is an arbitrary addition to the lacquer coating the wire....It is mostly there to make identifying defects to the insulating lacquer easier.

Application and frequency may make aspects more critical. I've been able to rewind 30's Philco antenna and osc transformer coils with a different (thicker) gauge and the same turns count and had them work.

I find it hard to tell some wire gauges apart. Often times it seems I'd need a low-power microscope to get a really good look. You're probably right about the color coating though, I've seen the stuff offered in blue as well.

I still need to wind a replacement chroma output coil for my Heathkit GR-2000 and now I need to wind a replacement for the blue second harmonic pulse shaping coil. The best I can do is try to match the wire gauge, wrap style, number of turns sometimes by sight only and the start/stop locations on the form. For the former I'm going to have to cut down another slug; on my last attempt the coil worked but the slug got stuck and then stripped, fortunately at a workable setting. Those ferrite slugs sure are delicate things, it was destroyed by a plastic tool.

Get some dial calipers and measure the diameter. There are tables online to convert diameter to wire guage.

Copy that, thanks.