That's a very interesting Firebird you have. It's not what I usually see, which is the "extra cost" type of special paint that is fairly common on 1969 Firebirds. When most people see PAINT-SPECL on their invoice, they assume they have a special paint car, but this simply means "extra cost" color, like Carousel Red, which was a $12.64 option.
Your car, on the other hand, is a true special paint car, identified as SOLID SPECL. This is a color that was not stocked in the Firebird plant (Lordstown in your case), so the plant had to have the color mixed or shipped in. The assembly line used to cringe when they had a special paint car, because this meant that their paint guns had to be flushed and filled for a one-time paint job, then flushed and cleaned again to return to regular paint production line colors.
Your invoice appears to have a billing error, which is rare, but not unique. It appears the SOLID SPECL was billed twice. The first line at $100.05 is the correct one. That was price for special paint on a convertible or a vinyl top car. The second time SOLID SPECL shows (highlighted) is the error. That would have been the price for special paint if they had to paint the roof too, such as a hardtop (without a vinyl top). It appears they double billed it, and they corrected the invoice on 04/09/69. This was to credit the dealer (Al Gallman Pontiac) for the billing error.
Pontiac used paint code "1" when special paint was used. The box on your invoice that shows "11" is actually a "1" followed by a "1". The second "1" is the code for a white convertible top.
The handwritten part on your invoice appears to be a paint code reference of GM?2?7685 (the question marks are the unknowns, I cannot make out the numbers). The last part of that line appears to be shorthand for "pricing error".
There's no way of knowing what color was used on your car without a build sheet, unless you can make out the handwritten note part more clearly and it proved to be a GM paint reference. However, pink is a definite possibility based on what you've uncovered so far. The build sheet would tell us the full story.
Hope that helps,
Mike"
With the history of this vehicle, all of the rust/moisture on and in this car, the build sheet has probably deteriorated many years ago. So, still in the same place.