Okay, Slime people bleed water essentially, when they bleed it puts the water overlay on a tile
Space lube does not have an overlay that I have EVER seen, it is invisible
Now that all of that is out of the way, it really should have an overlay telling you where the heck that asshole chemist put space lube so you can avoid it and taking a bruise to your noggin
Maybe similar to the water overlay, only light blue so it's a little more noticeable?
If the water overlay isn't already greyscaled, it would have to be though