Can I Put in a New Pair of Invisalign Trays when the Old Ones Blue Dot Has Faded All the Way?

Actually she is using invisalign (Invisalign Teen) has a blue dot to indicate compliance.  It does not matter to be honest.  As long as you have been wearing the recommend timeframe I would change and make sure they fit correctly. If they do, then switch, if not call your dentist

You seem to be using different clear appliance system then Invisalign. (Red, white and blue?)
Invisalign aligners do not use blue indicator dots for monitoring. You should check with your treating dentist to be sure prior to proceeding with your next set.

If your doctor scheduled you to change your aligners today, then I would change them today.  If you have been wearing the aligners as prescribed, the blue dots usually fade, but not always.  It doesn't hurt to wear the aligners extra days, but probably not necessary if you have been following your doctors orders.