Yamaha Rhino Fuel Injection 700 FI YXR70FY Manuel Du Propriétaire page 354

Inspection
The spark plug is an important engine component
and is easy to inspect. The condition of the spark
plug can indicate the condition of the engine.
The ideal color of the porcelain insulator around
the center electrode is a medium-to-light tan for a
vehicle that is being ridden normally.
You should periodically remove and inspect the
spark plug because heat and deposits will cause
the spark plug to slowly break down and erode. If
electrode erosion becomes excessive, or if carbon
and other deposits are excessive, you should re-
place the spark plug with the specified plug.
Specified spark plug:
CPR7EA-9 (NGK)
8-61