Donald Qualls
Subscriber
Blue antihalation is a known feature of Fomapan films, at least in 120 format (not in sheet sizes, as I recall, and I don't recall seeing it in 35mm). The first bath you give when processing (whether a prewash or developer) will pour out with a strong blue color, slightly tinted toward green. I recall seeing that color on Lucky film, fifteen years or so ago, as well, bright blue base side.