Why is there a small amount of milky substance on the cap of my power steering fluid?

Once you get watery liquid into a oily liquid its very hard to get out, you had it flushed out but still may be some residue left in resivoir or possibly the weather could be causing condensation inside the cap. I have noticed on alot of ford rangers if you check the oil you will sometimes see condensation on the oil stick and also alot of times if you open the oil cap you will find condensation on the bottom of the oil cap it is also milky looking due to being mixed with an oily substance. Is the power steering fluid milky looking also, if it is it may need to be flushed again.