RE: Soil/substrate

I was talking to a couple of Civil engineers at a worksite near my home which 
is littered with red-coloured earth.
I enquired whether the soil was pure laterite - the answer was that they 
couldn't be sure until they did a full soil analysis.  I asked further whether 
it was possible to determine whether a soil was laterite by the looks - they 
said "No".  Their reasoning is that there are a number of soils which have a 
red-coloured base.  The alternative method was to look at a geological survey 
map which would show the composition of soils in particular areas.

Is this true or are they just spoofing me?