What does OES stand for? Why would this take the fun out of traveling?
CalOES is the California Office of Emergency Services.
They are the Emergency Management Agency for the state.
Among other things they do radio systems for some state agencies, they have some fire engines, mobile command posts, etc.
As for taking the fun out of traveling….
Looking like an emergency vehicle often results in other drivers doing silly stuff around you, like driving a few MPH below the posted speed limit, won't pass, etc.
A plain white vehicle blends in well, most people don't take notice, they leave you alone, don't drive like little old ladies around you, etc.
Logos and names all over the vehicle also tends to make you an easy target. Drive 5mph over the speed limit, you get reported. Stop for lunch, and someone complains about state vehicles being used for "lunch runs".
I like my plain white truck. It's got exempt plates, but most people never notice. No logos, no blinky lights, no crap.