I'm pleased to report that the extra parts I ordered from Aliexpress finally arrived and I was able to replace the deficient panels and hinges. Here's how the ship looks now. The only thing I still need to replace is the cockpit windscreen (I'm using the round skylight from the Sanctum Santorum set, temporarily).
Here's the overhead view and you can see there's no visible off-colour body panels.
This view is the underside of the TIE bomber.
There were eleven panels that were dark gray instead of light gray. I ended up ordering 10 pieces of the light gray panels for $1. As a result, I have one panel that is still dark gray that hasn't been replaced. The pic above shows where it is.
Finally, here is how the rear of the ship looks after replacing all the hinges on the corners where the fuselage meets the engines. The hinges cost me about $2 for 20 hinges, so the total cost of the fixes for the TIE bomber was around $3 shipped.
Here's the link for the parts I used. They were the cheapest I could find off Aliexpress, but if you see a better deal, go for it.
Two piece hinge (set of 10). https://s.click.aliexpress.com/e/_dSixodA
Light gray curved panels (set of 10). https://s.click.aliexpress.com/e/_dXI0T7e
If you are interested in getting the not Lego set of Jerac's Tie Bomber from Aliexpress, please follow the link below.
AliExpress.com Product - 1494Pcs DIY MOC TIE Bomber Small Particle Building Block Model Compatible Legged 13952