As long as they were pressure canned for the required period of time, they should be just fine. I think the milky color of the canning liquid is just the starch, which has leached out of the potatoes.

Annie

Agree. The starchy liquid is normal. It is why, after opening the jars, it's recommended that you rinse them with fresh water before using them.

You don't mention it but I assume you filled the jars with boiling water before canning them?

Dave