Hi Darren,
It's not you, it's your car
What you have there is a very unusual vehicle.
If your car's ID plate has just a single, seven digit number that starts with 740, then what you have is a factory original replacement shell. That means the car was rebuilt early in its life with a replacement body shell from the GM-H factory. As a result, there's no colour or trim information, which unfortunately means there's no way of knowing the original colours, since they've gone with the (presumably written off) original body shell.
But on the other hand, you have a seriously rare vehicle. I've been involved in the FE/FC movement for nearly 30 years, and I think I have only ever seen two other cars with replacement shell ID plates.
Hope that helps, and welcome to the forum.
RET