Aquí un comentario sobre el tema, en la Wikipedia:
Tinting was utilized for years up until the early 1950s in select sequences, full monochromatic pictures and short trailers and snipes. MGM invented an interference-free toning process, which was used extensively in films such as The Wizard of Oz (1939) and Warner Brothers's The Sea Hawk (1940). Many MGM movies of the 1930s carried a sepia-like tone called "Pearl".
The Technicolor Corporation continued to experiment with both tinting, toning and colorizing. The last reel of Portrait of Jennie (1948) contained both green and amber tints by Technicolor. Mighty Joe Young (1949) displayed a further concept of tinting by Technicolor, with various shades of red, orange, and yellow creating a fire-like effect for the last reel. The Cinecolor Corporation also created similar effects, and sepia-toned several films as well as tinted select scenes in chapters of the 1951 Columbia serial Captain Video.
Y en una entrevista a Harryhausen habla del tema:
dOc: On the commentary for Mighty Joe Young, you mention that the finale with the fire was in Technicolor at one point?
Harryhausen: Yes, we were going to shoot it in Technicolor at one time, but the budget was too high so they had to cut it down. On the early release prints, Technicolor injected the color. It wasn't shot in color. It was shot in black and white and Technicolor had a process of putting in the red flames and the yellow flames in some way in the black-and-white print. But most prints don't have that now. Only the first release.
dOc: Do you know if any of those still survive?
Harryhausen: There is one that's colored all red, and it's not the same. I don't know whether they've survived. Perhaps someone has some somewhere, maybe the Academy or the BFI. You seldom see it with the color in the last reel.
Es decir, deduciendo de ambos textos, se entiende que la idea era rodar la escena del orfanato en Technicolor, pero al final les redujeron el presupuesto. Así pues, la escena se rodó en blanco y negro, y después, mediante un sistema técnico especial elaborado por la casa Technicolor, le "inyectaron" color, rojo y amarillo en concreto, para que las escenas dieran la impresión del fuego a color.
Al parecer, no sobrevive ninguna copia con esos "tintados", por lo cual esta copia ha coloreado de ese naranja fuerte la escena para aparentar el efecto.