For what it is worth, my understanding is that '67s had brake fluid initially and later switched to ATF. I bought my '67 in 1980, so it likely had the "original" fluid in it, which was the straw-yellow color of brake fluid. Sometime later, one of the plastic lines broke, spraying fluid onto painted surfaces, definitely screwing them like brake fluid would.

I just re-filled my system this summer and put brake fluid back in it; according to my copy of the '67 Body by Fisher manual, it calls out refilling the "resevoir unit with specified Delco No.11 Hydraulic Fluid (GM Hydraulic Brake Fluid Super No.11 or equivalent)." (page 13-27, Installation section #1).

It's been so long since I've dealt with ATF fluid in a GM car, I don't recall if all types of GM ATF fluid were alway red in color; hopefully I haven't screwed up my pump & cylinders....