https://www.jamesallenonf1.com/2018/12/pirelli-reveal-compounds-for-opening-rounds-of-2019-f1-season/
Pirelli have revealed the first tyre compounds that they will use under their revised system, brought in for the start of the 2019 season.
In a bid to simplify the F1 spectacle for fans, Pirelli have introduced a revised system where only three colours will be used on the walls of the slick tyres; white, yellow and red.
These will indicate hard, mid-range, and soft-compound tyre on all Grand Prix weekends, despite the exact grade of tyre still varying from race-to-race.
An additional system will be used to specify the compound of tyre, ranging from C1 to C5. C1 will be the hardest compound, and C5 will be the softest.
In 2018, a seven-tyre compound range was made available, including four types of ‘soft’ compound; soft, supersoft, ultrasoft and hypersoft.
Under the simplified version, three of the first four rounds have been allocated the middle three tyres; C2, C3 and C4. Bahrain will use a harder range; C1, C2 and C3.