I know I am somewhat of an old Fuddy-Duddy, but I would never put a properly heat-treated alloy steel frame back in the furnace just for "Color". I am also somewhat hesitant to even do it to plain carbon steel. "Any" time you take a piece of steel above it's critical temp some "Risk" is involved, regardless of what anyone may tell you. Maybe they've done a thousand with no problem, "But" #1,001 may just be the one that warps badly or even cracks.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra