Depending on if it is a revolve or semi-auto, condtion, box, accessoires, manual, etc., it could range from a few hundred to multiple thousands of USD.
Proofhouse.com has Colt sn data.
Impossible to answer without a detailed description and the serial number.
50-2000 usd
Colt 1911 .45 serial # 171885 was manufactured in 1917.
your colt was made in 1918. However, value depends on overall condition of your pistol.....
You will have to call Colt to find out.
A Colt government model .45 with that serial number was made in 1917.
The age and value of a colt .45 peacemaker serial 180356 are about 1900
Colt army .45 with that serial number was made in 1944 by Remington Rand for Colt.
50-500 usd
10-10000 USD depending on specifics
-60-600 USd