easiest way is to google for the wiring schmematics of the motorcycle in question.
(best the exact year and model) then you not only know where but you also know what color
But, any fzr 600 that's reasonably close (not a decade younger/older) should do.
PS since when does all wires of the starter are wired to the rectifier?? (simple anser: they don't!)
the rectifier has two IN and two OUT terminals, AC comes from the alternator and is (hence the name) rectified to DC power.
Those two are more often than not red and black sometimes orange and black
(alternator usually uses brown and white sometimes brown and blue or alike)
Anyways, a multimeter (set to DC Voltage) should tell you for SURE which one is which,
but only if the engine is running..
the smae Multimeter set to DIODE test can tell you how the diodes are facing inside and that works well with a non running engine and no power at all
So.. just use a multimeter to find the DC lugs on the rectifier.
Now...
those two wire straight to two wires on the starter (plus on plus, minus on minus... straight forward, ain't it?)
the last (usually a bit thinner than the other two) is the solenoid switch.
that's wired straight to the starter button. (that's again a 12V+ signal.. but much less amperages needed to power the solenoid

)
button pressed, solenoid closes, starter runs.. button release, solenoid openes, starter disconnects ...
done
'sid