In the color system if I mixed the color of silver and the color of
gold what color would I get as a result ?I need a  scientific
explanation  . Can I know the wavelength of them.

I'm not really sure myself, but check this out, i think it will be very helpful.
http://en.wikipedia.org/wiki/Color#Color_perception

Hi Angel,
I wasn't clear from your question if you are talking about mixing gold
and silver or if you mean mixing gold and silver colors somehow:
paints crayons, whatever.
Since you ask for a scientific explanation, I expect you mean the former.

Mixing gold and other metals accounts for the different shades of
gold, "red" or "pink" gold with copper, paler shades of gold, with
white metals: nickel, silver, palladium.

http://www.24carat.co.uk/whatiswhitegold.html 

This was the best site I found (but there could be better ones) that
explains the subject.  Somewhere on it, it mentions the fact that
nickel (I believe it was) has a stronger influence on the refraction
of light.

I hope this is of some help.
Myoarin

The alloy of gold and silver is called 'electrum'. Appararently, this
occurs in nature.

Mixing gold and silver paint will probably yeild different color
results than mixing gold or silver metal.

The color and reflectivity of gold and silver have to do with the
properties of their conduction band electrons. The forces on the
electrons are dependant on atomic mass, number, etc...Silver is
(generally) a broad band reflector. All wavelengths are reflected in
equal proportion. Gold more effciently reflects colors of longer,
redder, wavelengths, and thefore appears yellow.

The best way to measure these colors would be with a spectrometer
coupled to a reflectance probe. e.g.

http://www.oceanoptics.com/products/reflectionprobes.asp

A better method would be to use an integrating sphere, which is what
is often used for LED and pigment color measurements. e.g.

http://www.labsphere.com/

Following up on myoarin's link.....

http://www.24carat.co.uk/whatisgreengold.html

Green gold alloys are made by leaving the copper out of the alloy
mixture, and just having gold and silver. In most cases, it is more of
a greenish yellow, rather than what most people would describe as
green.
Eighteen carat green gold would therefore contain:- Gold 75%; Silver 25%

Although, to me it looks more like pale gold.

I'd suggest going to a jewlwer and asking them to compare some samples.