Dan,
well, if they were talking abt a 'sandy' color, it was probably a "dunkel gelb" (dark yellow)
equivalent. it is a kind of yellowish tan. some see a hint of 'greenish' in there.
i don't, but colors are funny that way. :-)
this page has some color chips:
http://aura.olomouc.com/ukazka_4en.htm
i think the left most dunkelgelb is in the ball park.
i believe in scale effect too, tho i am not sure how light you would have to go
for 1/144 ! you might want to try lightening w/ a buff or tan instead of white too.
the red brown and 'grun' are in the ball park for the other colors of the three color camo.
in the Tamiya paints i use XF-61 Dark Green and Red Brown.
German tanks w/ three color camo frequently began as straight dunkelgelb vehicles.
the red brown & green were issued as concentrates made to be thinned w/ gasoline and sprayed on. the realities of war meant they were thinned w/ gasoline, waste oil, water, diesel, etc . . .
and they were applied w/ spray guns, brushes, brooms, mops, rags, hands, etc.
the variation of color & pattern are countless.
hope this helps at least a little.
on the PE - welcome to the club!
:-)