The color in the grease is merely a dye added by the manufacturer.
All of out blue Mobile grease will turn black after a while.
We use Mobil PolyRex EM which is a polyurea synthetic electric motor grease which has a higher break down temp and almost all motor manufacturers have migrated to this over the years.
Probably it matters little what grease you use since these trailers probably suffer more from disuse and use.
That being said I saw three (boat) trailers with either smoking hubs or stopped on the side of the road with spindles destroyed and bent form the heat.
But this is boat trailers which probably had the hubs immersed in salt water while still warm from towing to the ramp.
Here is a situation where bearing buddies or EZLUBE is really helpful.
If the bearings are over packed then the excess grease will make them run hot untill it is forced out, either through the outside vent in the EZLUBE or back into the Bearing Buddy or through those new seals you just installed. This is most likely the main cause of grease getting on the brake system from the hub.
The beauty of the EZLUBE is that the excess grease has a known path to escape
if you manually overgrease or pump it through with the grease gun.
After you service the axle
with EZLUBE if you use the grease gun and don't pull the hub and do it manually there will always be some more grease that will be forced out.
Remember the balls in the races (or rollers for that matter, either way) do not run in grease, they are lubricated by the oil that is carried in the grease and flows into the races over time from being next to the races and in close contact.
The rolling elements make clearance through the grease if you will.
Over greasing forces too much grease within the races and the churning action will cause the overheating and very likely cause the soap and clay to separate the oil and actually end up starving the bearing from oil it needs to lubricate.
The bearings should never be hand packed more than 1/3 full to allow the room for the bearing to run.
When we grease motors here in the plant we have temperature readouts for both ends and we add the recommended amount and the bearings run hotter for several hours until the excess is pushed out of the grease relief ports.
We are transitioning to an ultrasonic measurement of the bearing noise which indicated when the bearing need a little more grease and we then add it until the ultrasonic nois level drops to avoid over greasing and track the actual bearing condition.
If I were to regrease my bearings I would be tempted to use the Mobil PolyRex EM, but this and the more often used lithium based greases are incompatible and should not be mixed. However if you carried your own grease gun it would definitely be better.