How many levels is the typhoon?

Typhoon warning has four grades: blue, yellow, orange and red. Typhoon blue warning means that the average typhoon wind force is above 6; Yellow warning means that the average wind force of typhoon reaches 8 or above; The orange warning indicates that the average typhoon wind force is above 1, and there may be flash floods at this time; Red warning means that the average typhoon wind force is above 12, and people need to be prepared for evacuation at any time.