Hi,
the Austrian army was supplied with Leo 2 by the Netherlands. These tanks are painted in RAL 6014 (in Germany called GELB-OLIV) the early Bundeswehr colour, because they were delivered from german Bundeswehr stocks. You can use Revells NATO-OLIV (R 46 ???) for a faded look of your model. Or you watch under www. modelversium, klick links and search for modelcreator Jens Popp colours (JPS). He has the exact (and other, like FS, BS) colour in his inventory.
Good luck.
armyarne