[Jonathan L.]

The Max&Min function shows up as a bit lighter than the other functions for me too; but it still works. As long as the code runs and you're not getting any other errors I wouldn't worry about it. I think they just made the color of the lines in it a bit lighter than everything else.

Side note:
Technically, the Max&Min (and any other block that cannot be opened) is a function, not a VI. Basically, it's as close to binary as you can go in LabVIEW before getting into the source code of LabVIEW itself.