Im a hydraulics engineer and can confirm the ISO 10w and 15w comment made.
Sod all difference in them and the OM is equivelant to an ISO 13.
We use mainly ISO 46 and ISO 32 all day long, the 32 goes in the older machines with a bit more wear in them!
Dont worry about mixing ATF oil, it mixes with all Hydraulic oil grades.
Just because its red doesnt mean its ATF either, JCB put a red dye in their ISO 46 and tell you that you need their "special" oil only and charge you the earth for it!!! LOL
I have also seen it in GREEN and BLUE!!!!
At the factory they only put ATF in the hydraulics of most Cherry Pickers because of the lower viscocity. Only because they dont know the climate the machines are going to, could be hot or sub zero! We always top the tanks up with HYD 46 (ISO 46) as recommended by NATIONWIDE ACCESS who supply them!
Any problems let me know I have a good source for oils and lubes if required.