The blue street juice is for high traction track, the purple one for low and medium traction.
We often use the purple on the rear, and the blue on the front. This makes the car more smooth to drive.
Apply rear tyres for minimum 45 minutes, and wipe off 10 min before race and let dry.
Apply front tyres 15 min, and dry 5 min before.
After each run clean the tyres with motor cleaner, this to wipe of all residue.