1986 Sierra Classic original paint color code?

[Niddrie]

I bought this 1986 GMC Sierra Classic last Monday. It has very little rust, the only major rust is showed in the second picture. I want to remove the rust and restore the paint, but I am having issues finding the right color. I'm pretty sure the truck has original paint, aside from the dark grey paint on the bottom of the truck. I've tried searching for the color code, but the one I found looks a little too light for the truck.
It's called Light Blue Metallic 21/WA7470
Here is what it looks like

I just searched again and found another paint for that year called dark blue metallic and it looks a bit closer. Here are the two colors side by side

So which paint is the right color?
Any help would be greatly appreciated!