(used for Turmoil in Gotham as well):

Violet=We pose more of a threat to them than they do to us
Indigo=Little threat
Blue=Potential danger
Green=Direct threat, some action required
Yellow=Armed combat/war initiated
Orange=Full war declared, main military priority is ending threat
Red=Annihilation of one side is necessary for the other to survive

(used by police and national guard):

5=No threat
4=Surveillance required
3=Criminal
2=Armed repeat offender
1=Immediate danger to public
02=Armed repeat offender, lethal force authorized
01=Immediate danger to public, lethal force to be used

Green=Barely any to no danger
Yellow=Mild threat
Orange=Very unsafe
Red=Immediate danger
Scarlet=Widespread danger to everyone