MC;
I have not witnessed any color case hardening of fireframes frames. My experience with both heat treating & case hardening has been in the machinist trade with non firearms related parts. While I was a machinist & not a metallurgist I do know enough about the process to know that to make a flat out statement that a piece of steel which has been heated to its critical temperature & then given a sudden quench "Will Not Warp:" is basically absurd. Take it for whatever its worth to you, it didn't cost anything.
Warping can occur in any form of heat treating. With case hardening as the hard part is only on the surface with a soft core beneath they can be Bent back into shape. Of course proper procedure, including blocking, can minimize warpage but is no absolute guarantee against it occurring.
Personally when I have a good fitting, smoothly working gun I am not willing to chance any problems just for the sake of color, I still have the hard case, it is not lost with the colors. There is even a remote possibility the frame could "Crack" in the quench. To me it is just not worth the chance.
