Murray Greys vary greatly in color,  they can be anything from White to
Black with many shades of brown in between , but they will always be a
solid color with no white body spots.  White is only aloud on the belly from
the navel back.   
Some Murrays'  have small circular patches of off color body hair, these
are natural birth marks.  They usually appear as tan and have no white hair
or white skin underneath.

Murrays can also be dappled, I was told an old Australian tale about
dapples are a sign of a good milk producing mother.   photos below.

No white hooves or skin pigment.
Dark skin is a must, even the silvers have a dark hide and are dark around
the eyes, muzzle and hooves.  Most Murray Greys test as Homozigous
Black.  Every once in a while one comes along with a red gene.
Calves with pink skin and hooves can't be registered.

No one knows how the Murray Grey Color Genetics work, but many have
tried.  If you breed black to black you usually do get black.  If you breed
silver to silver you usually do get silver.
BUT...  Not always.
People have gotten Silver from Black parents, and last year my cow
Pecan (who is dark) bred to a Silver, had a black.  The Duns/Browns
produce any color.

I took these photos at the 2007 Nationals.  You can see the different
shades of silver, I only got the 1 dun calf and 1 black in the group.  I didn't
get any of the brown chocolate or almost black ones.
Below are coat patterns of a Dun and a Silver with Dapples. The Dun Cow
(JB Romance Rose) not only has light dapples, but a few black ones also.