Why do Ambulances and Fire Engines in Spain use orange/amber emergency
lighting, the same as break down trucks and refuse collection trucks
etc ?

Hello, delone70:
  I'm spanish and I would like to ask you, why there must be a reason?
Do they must be different?

Regards.

After a recent trip to Spain, I think there are reasons why they
should be different.

If you cant tell an emergency vehicle by sight you tend to be able to
tell by the sound..... and thats problem number one. In the area I
stayed there were 3 hospitals nearby and the almost constant drone of
Sirens was very annoying. This may be "background" noise to residents
(but I doubt it), but it is unnecessary all the same. I'm sure the
"Orange" lights contribute to this greatly.

Problem number two comes from a road users point of view. One day I
spotted orange flashing lights in my rear view mirror, knowing it
could be a breakdown truck or a fire engine I kept checking and
checking. Unfortunately it was a fire engine only I could not tell
that until he was stuck behind me at a junction, I only heard the
siren when he was immiediately behind me.

With the above in mind (and common sense), should they be different ?

Hello, delone70:
 Well, probably this may sound strange to you because you are not
spanish, but we have not many problems to distinguish between the
sounds of:
-Police sirens
-Ambulance sirens
-Fire sirens

There are two groups of colors: Local police, national police and
guardia civil (blue or green) and ambulance, fire fighters and trucks
(orange).

But maybe, the reason to put trucks the same color than ambulance and
fire fighters could be, that the lights (without sound) on trucks were
imposed by government few years ago, maybe if some problems arises in
the future due this, the law changes. Right now, to be safe driving in
Spain, if you see some flashing lights on your back, be careful and
keep looking until you see the vehicle, because, there are times, for
example, police just flash lights without a sound.

Regards.