The palette (colours) appear normal (greens, flowers, colour of the animals), so I consider it might be flare judging by the position of shadows; the noticeable blue tone is characteristic of E6 emulsions where there is a mix of shade and bright sunlight. But all the opinions you read here will be speculative rather than definite, without actually physically examining the tranny!
Velvia stains pinkish when there is a chemical shift, or green (such as very long night exposures). Have you seen this on any of the shots on Velvia from the same or similar position with the sun in front of but just out of range of the lens?
Film that has been subject to cycles of heat and high humidity in other words,
damaged, will probably turn up a fault like this. My first (and only!) roll of E100VS came back with a terrible overly brown look about it. However, my own Fuji films have been subject to many cycles of heat, cold and humidity and only ACROS 100 has dared throw up faults that are clearly due to these conditions any problems that I do see with E6 are a result of the lab, which thankfully is free of errors so far!