So we have sodium and mercury lamps. Which heat up a vaporize said metals to form plasma arcs.

What is stopping us from upping the heat and vaporizing say... copper, iron, tin, maybe even uranium, gold, lead, Into a plasma arc?

What colors would be produced by such vaporized metals?

I am sure there is alot of fundamental knowledge I am missing. But from my understanding with a thick enough quartz wall and large enough electrodes or electromagnet, it maybe possible to vaporize anything into a plasma state for atleast a short while yes?

I am assuming this has been done somewhere. But I am having trouble finding examples on the web. And finding pictures of said discharges is hard because alot of the search engines also pull up pictures from movies/news articles/market listings for unrelated stuff.

The most important thing in light color/temperature (and light source technology !) is diversity. You may not like 6000K..6500K lights, but the fact they exist and are installed somewhere, make 2700/3000/4000K lighting in other places not be taken for granted, which is an important part of the lighting looking good

I’ve found they only tend to stay white longer as they age?
When new all sizes to me have the same ‘white’ time when running up.

That is correct.  Especially for high pressure sodium. 
Some brands will start up and warm up quicker as well.  Sylvania would warm up fairly quickly versus GE which wasn't bad.  Philips seemed to take a little longer. 

I myself am not happy with the 5000 and 6000k selections.  I much prefer 3000k, 3500k, and 4000k.  I order most of the LED lights I use now from 1000bulbs.com where I can select which colors I want, or get multi-selection LED tubes with those color selections, but I have noticed at Home Depot and Lowes that they are selling color selectable with those 4000, 5000, and 6000.  6000 is flat out stupid.  I know of no environment where it looks better than 4000 or 5000.  3500 is what I consider neutral white and it has become my favorite to use in many buildings, however- there are still some buildings where the color of the carpet and walls will dictate using 3000 warm white or 4000 cool white for best results.  I like having a relaxed inviting color tone like 3500.  4000 works great in building bathrooms and shop areas, and 3000 and 3500 works great in classrooms and offices. 

Bumping this as I am still looking for one. If anyone comes across one please PM me!

An grey Fisher Pierce would probably look decent and was available in the 70s.

There's some from the 90s for pretty cheap:
https://www.ebay.com/itm/305372491904

The oldest one I found was this from the early 80s but it's much more expensive...I personally wouldn't get it.
https://www.ebay.com/itm/276701670178

I've looked for those but I can seem to find one. I mainly going after those tall blue ones that they made around that time such as this one in this eBay listing: https://www.ebay.com/itm/167947718817

Well, Fisher Pierce made PCs in the 70s. I'd say go for either them or Area Lighting Research. My personal preference: Fisher Pierce. They often pop up for dirt cheap on eBay. I have one from 1979.

Was wondering if anyone has or knows of any era appropriate 1970s photocells. Preferably NOS to complement my mostly restored OV-25.

Thanks, John