Tokyu 8500(?) with green stripes?

[railsquid]

Recently I've started using the Hanzomon line on a regular basis, albeit for very short trips, and am happy to note that it is not yet entirely dominated by brushed-aluminum E231 (?) derivatives. Coming home this evening I was slightly bemused to hop on a Tokyu train with a two-tone green stripe along the body (until now all the old Tokyu cars I've see have had a two-tone red strip). Is there any story behind that? I wasn't really awake at the time so didn't think to take any pictures, but the car number started with "88" (which would seem to indicate a 8500系), and the construction year was Showa 50 (1975).