Pentosin CHF 11S will turn a rusty red over time................

"Pentosin is a large temperature range (Multi-viscosity like) Hydraulic system fluid.
Pentosin 7 is a mineral based oil and Pentosin 11 is a full synthetic.
ATF is basically a high detergent 20w oil with the lubricating property additives modified to make it Dexron or Mercon.
The additives and detergent levels in ATF make it very "Poisonous" to a Pentosin based system. Seal leakage is the result of mixing them.
Pentosin is a pale green out of the can but will turn a rusty red over time. It is NEVER bright red."