The "blue" switch is a popular universal replacement switch for vintage Marantz stereos. It fits most models. It will be a direct fit with a handful of models. The rest will require modification of the aluminum button to fit the shaft. Or the shaft diameter will need to be increased to fit the button. And sometimes the switch will be rotated ninety degrees from the original.
About Replacement Switches
I don't think there is an ideal replacement power switch. But they have to be replaced so we use the best fits we can. Marantz used several different switches, sometimes on the same model with running production changes.
Wiring Replacement Switches
At first the new replacement switches look confusing as they have more posts than the originals. The pair furthest back from the front of the switch are for power out (orange, brown, or yellow depending on your model). Say it is the brown wire. You can strip it long and bridge it across the rear pair of posts. Say the orange wire is power in. Strip it long enough to bridge across the middle pair of posts. The pair of posts nearest the front of the switch are not used.