Join Date: Jun 2016
Location: Orange County, CA
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
Most jurisdictions regard red flashing lights as illegal on anything except emergency vehicles and non-SPAB school buses. This law obviously is full of holes and is enforced either unevenly or not at all, but it could still be a reason for an over-zealous cop to be difficult with you. You may want to check your state's vehicle code and see what it says.
FYI, my rear red flashers are now repurposed as extra high-mount brake lights, but they only work when the fog lights are turned on. Is this 100% legal? Maybe, maybe not. In practice I'm not worried about using them in very poor visibility.