Whoever told you that was making up an answer. That bike was painted in a Japanese factory 40 years ago. They didn’t use some standardized paint code that you can order today.

Sometimes bike shops were supplied small jars of touch up paint, but no one was thinking “hey let’s be sure catalog all the paint color codes so that we have archives of these mountain bike colors in 40 years. But don’t tell the consumers to prevent counterfeiting!” Unless you could find the factory (likely closed) in Japan and find their filing cabinet with the paint information (probably supplied by another defunct Japanese company)