The reason that the lights don't appear blue is that the velum paper that Marantz used as a diffuser has become dis-colored. If you change that out your lights will be blue again.
Since these units are thirty years ago, or so, some of the previous owners may have used replacement bulbs that were the wrong voltage, which got too hot and caused the velum paper become discolored. Which in turn makes the lights appear green instead of "Marantz blue". In the worse case using lamps above 250 ma may melt the plastic lamp hosing.
In my 2285 I have replaced the "fuse lamps" with LED lamps. The LED's run cooler and never burn out. With the LED lamps the color is slightly deeper blue, but for me was worth it since I hate changing bulbs. I recommend these for easy maintenance.
If you do use the original "fuse lamps", never go above 200 ma - 250 ma. The original spec is for the 200 ma bulbs, but these can be hard find.
If you need sources for either type of bulb just PM me & I will steer you in the right direction.