Turning black is an indication of your pet absorbing as much UVB as it possibly can!!
You do have some nice UVB lights shining down on him(her)???
Sometimes before a shed chameleons dont eat prior to the event!!!
How long has your pet not been eating???
There is a form you can fill out to aid in the help process by the knowledgeable people on this forum,,,heres the link,,,,just copy and paste the form to a new message in this thread and your answers will help them visualize how your pet is being kept(husbandry)!!!
This is the link
https://www.chameleonforums.com/how-ask-help-66/