Are you asking what color to heat it for annealing? If it was me I'd simply fire up the lead pot and once it reaches around 700-750 degrees I'd put the hardened part in the lead for about 5 minutes to slightly anneal it.

In regards to the color hopefully you can see it on the right hand side of this chart. 
If click on you should also be able to enlarge it.

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I am new to messaging on this forum, but have read allot here and enjoy it very much. 
I do my spring tempering by polishing my springs before they are oil quenched and polished again afterward to get the part nice and shined up before tempering. I use a jewelers torch and temper them by sight. The polishing helps me see the color changes clearly. the part goes from a blue to straw and then just as the straw disappears to a purple/blue I stop heating and let air cool.  It changes quickly and it took me time to get it down, but have made many springs now and have had excellent luck with them.

ssdave wrote on Jan 27^th, 2023 at 10:01pm:


this is good reading. notice how toughness goes up as hardness goes down? you can think of it as toughness resists breaking while hardness resists bending. I made my recommendation considering that the thin edge of the ejector needs to be hard enough to resist bending and tough enough to not break both considering extraction of a hard extracting case. this chart from daves link shows both hardness and toughness graffs