To update route configuration, use the command route/update_config:

svc=route/update_config&params={"itemId":<long>,
				"config":{
					"color":<uint>,
					"descr":<text>,
					"units":[<long>]
				}}

You may create route using core/create_route.

{
	"rcfg":{	/* route configuration */
		"color":<uint>,		/* color (ARGB) */
		"descr":<text>,		/* description */
		"units":[<long>]	/* array of units IDs */
	}
}