Looks a lot like cutting oil mixed with soluble coolant, regular oil and lots of rust and dust that's being floated out by the water from numerous rains. I actually worked on a lathe with very similar looking coolant in the sump in use at a local factory, and it was mixing into the headstock oil via a hole in the joining reservoirs!! nasty stuff. Real shame to do that to any machine that has any chance of being useful again. Hopefully someone can save her.
The problem with most government surplus is when the equipment goes out of service it generally sets outside until the surplus paperwork is done and then even longer out in a storage yard. Summer time may not be so bad, winter in the north west is another thing. Some years back I purchased a large boring machine from the navy, my rigger told me he had to shovel snow off it before loading. I was not happy about the fact I was told it was covered outside. The sting wasn't so bad as I picked it up for 4,500 and the navy paid 280,000.