The little facets of the Technicolor Two Color system of which most people aren't aware. What surprised me the most was the large number of films made with the Technicolor Two Color System, 384. Most probably didn't survive to our day but still it was a very impressive effort that allowed Technicolor to barely amass enough resources to concentrate on developing a photographic system that would in time capture the full color spectrum. I also thought I heard that a studio executive ordered a Two Color print processed in some special way with a blue dye so as to allow for a more natural rendition of color with the limited Technicolor Two color system.
I have seen original nitrate Nitrate IB prints of three strip films projected by carbon arc and no Eastmancolour restoration that I have seen really manages to reproduce that look. However, some recent digital releases on DCP have come close.