No, the center cap on the gemini wheel cover is not intended to be removed from the wheel cover.
To be honest, when new, the lug nuts without the chrome covers look fine with the silver center cap. Perhaps over time the nuts and/or threaded bolts may rust, so the chrome covers are a cleaner look.
Also, if you do get the center cap kit, you must remove the center cap any time you want to put the gemini wheel covers back on. The only non-marring way I have found to remove the center cap is a 2.25" suction cup which can be purchased at
Harbor Freight.