The duration of the spell does not indicate the duration of the prestidigitation effects.It instead indicates how long you can create magical effects with a single casting.
Once cast, a prestidigitation spell enables you to perform simple magical effects for 1 hour.
The only mention of effects fading is at the very end.
Any actual change to an object (beyond just moving, cleaning, or soiling it) persists only 1 hour.
According to this, if you have 1 minute left on your prestidigitation spell, you can change the color of an object and it will stayed colored for an entire hour, even after prestidigitation spell ends.
So putting all this together, since there is no explicit duration specified for the fragile objects created by prestidigitation, do these objects last forever? And are they instantaneous duration or permanent duration? (The former is not dispellable while the latter is)