Overloaded Fuses will have a CLEAR window as the wire has broken without much heat buildup.
Short Circuited Fuses will have a DARKENED window as the wire has vaporized in a short amount of time.
The same situation I believe happens to lamps, although I don't have anything sitting here to check against. If a lamp gets broken due to being moved around when it's cool (no heat build up), there is no clouding of the glass.
When the lamp is broken while there's load on it, from a short circuit or whatever the case, it does cloud up the glass. I assume this is caused by the wire vaporizing quickly.