After further reading I'm keeping this fluid. The Kendall Hyken Glacial Blu is suitable replacement for Dexron III as well as PS fluid, so I'll have no trouble using it up. Actually I'll probably need more at some point, it is no more money that Dexron III anyway.

interesting reading at
Revised Summary of Citroën Hydraulic Fluids
and strelniks posts at
http://www.peachparts.com/shopforum/diesel-discussion/286321-whats-best-power-steering-fluid.html?highlight=kendall+hyken+glacial+blue
http://www.peachparts.com/shopforum/diesel-discussion/269716-1987-300td-self-leveling-suspension-fluid.html?highlight=kendall+hyken+glacial+blue
http://www.peachparts.com/shopforum/open-discussion/290880-hydraulic-fluid-question.html?highlight=glacial

He either knows a bit about hydraulic fluids or he's baffled me with his BS.