too soft...(imo)
for most racing in most conditions, the blues are most commonly used.
I have used grey's once or twice, when the track was wet, or very dusty.
combine the blue springs with 30 - 40 weight oil and 3 hole piston for outdoor asphalt as a good starting point, only go up in oil when grip level is increased (usually carpet or if the track is prepped with VHT, sugar water etc)