AFAIK, True Blue and Light Blue are the same color - ANA 501. I've seen it listed as either. It appears to me as more of a medium blue, but compared to Insignia Blue, I could see how someone might name it Light Blue.
I still suspect that if the fading, desaturation, darkening, and yellowing experienced by old color images could be reversed some how, you'd see ANA 501 or something similar on the tails. In addition, no documenter I've found referred to the tail color as any shade of green - only medium blue or light blue.