what is a silver tabby vs smoke or lilac

Can a breeder help me with the following:

What is the coloration difference between a
sliver tabby, a smoke tabby and a lilac?

My feral kitties have some type of silver/grey
in their line. all the tabbies are of 2 types:
either brown/sable/black or grey/smoke/lilac

The feral girl currently taming in my home
is an astonishing color. She is grey and
cream/white with darker grey NOT black
at all. The tail tip is a lilac color and the
banding on the tail is definitely grey on grey/lilac.

Her eyes are golden. She's a doll in a word.
There is a second kitten from that litter (now 3 / 6
months old) who is a bull's eye patterned grey/smoke
tabby.

I have no idea how common this coloration is,
but I personally have not seen it before. Last
year, there was briefly in winter - a cat that came
to eat. She (pregnant from what I could tell)
was a snowy white, with black spots, green eyes
and silver sheen. I thought at the time she HAD
to have some pure blood to achieve that coat/
pattern. That was what led me to wonder about
my grey tabbies. I wondered if they were her
get.

I've not seen her since - and suspect she either
moved on, was fixed and kept inside or unahppily
might have been hit by a car.

I'll try to explain from your description. Sometimes its hard without a picture as a person's interpretation of color is not always what you think !

Silver tabbys are basically a very white silver color (not greyish) with dark black markings.

A smoke would be white fur next to the skin with overlay of black or blue color on the rest of the hair. Smoke usually can be seen best when the hair is flipped back to reveal the white undercoat. Usually some ghost like tabby markings can be seen (mackeral or classic) but its not really a tabby cat. You CAN have a smoke with spots (spotted tabby) as in the smoke Egyptian Maus.

Fawn/Lilac is a "bluish pick" shade - kinda weird to describe. I'll try to find some pictures.

First some genetics:

http://my.net-link.net/~cwjohnso/genetics.html

Silver tabbys:

http://www.alken-murray.com/Barrymore.htm

Smoke cats:

http://www.cfainc.org/breeds/profile...ian-smoke.html

Smoke E. Mau:

http://www.geocities.com/embfc/

Fawn/Lilac:

http://www.chocolatecats.com/lilac-kittens.htm

Thank you Golden Kitty. The cat I saw was DEFINITELY a
silver Egyptian Mau. No mistaking the spots. Or the white
on black coloration.

The genes must have been passed down.. the kitties
I have are grey on grey / silver colors... diluted
tabbies of some kind. Not the usually black and tan
coloration..

I will try to post some pics of my lovely feral babies!