Hey,

take a look inside the texture folders,
the problem probably is a file called
F-18_Main07_T.dds.
This file contains the canopy textures.
In your first case, try deleting it (don't forget to back up the file)
If this doesn't solve it, try using the one from the standard finish livery (as this is also gray)

in the second case, make sure it is there. If it's not, FSX will use the one in the 'texture' folder, which is a gray colored aircraft.

If this doesn't solve it, can you post screenshots, and links to the used liveries, I will then try to replicate the problem on my pc.