The bug
The player model in the inventory (Both survival and creative) reacts to light level just like the player in the game. This means that when it's dark, the model in your inventory becomes dark as well.
How to reproduce
Open the inventory in any light level you are currently standing in. Then find a contrasting light level to stand in and open the inventory again. See how the model in the inventory either gets darker or brighter.
Thank you for your report!
We're actually already tracking this issue in MC-162013, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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