Mixing hydraulic fluid

[spruce Deere]

I think you will be fine. I would just stay with main brands like cheveron, unocal, mobil. They all are different colors but most will have same applications

 

[PILOON]

Of all the petroleum products, hydraulic oil is the least critical and cheapest.
If U wanted 'quality' you would want to go to a non detergent SAE engine oil and some equipment actually specifies that.

Got this from a petro engineer (a neighbor) that worked for Shell.
He ran his own tractor on SAE for ever.

They use 'oil' as it won't freeze, won't compress and does have some lubrication qualities and prevents components from rusting.
Water could be used for the actual power transmission were it to not lacking the other desirable qualities.