Oh, nice find! From that bug report:
This seems to be exactly what is going on with Panda, judging by the output you posted:
PFD cColorBits: 64 R: 16 G: 16 B: 16
Does it work when you set the precise following settings in Config.prc?
color-bits 8 8 8
alpha-bits 8
Panda does give priority to pixel formats that match the requested number of bits precisely, but it may not be enough to cause it to win out over the 64-bit format.
We’ll need to do something similar to what Blender does: down-prioritise pixel formats higher than 32 bits per pixel.