It seems highly unlikely that the paint in that bottle retained its original color-affecting properties over all this time. When using it to touch up machines

It seems highly unlikely that the paint in that bottle retained its original color-affecting properties over all this time. When using it to touch up machines that have approximately the same age, you may get lucky and the colors resemble eachother, as appears to be the case in the article. Attempting to determine the color identity (e.g. pantone or hex) of apple beige however seems impossible using old paint. I am not a chemist though, so it may be possible that this paint has chemical properties that cause it to retain its color-affecting properties over long periods of time. I just think it's unlikely.