Stephanie, as a fellow amateur researcher, here are a couple of thoughts in addition to what Andrea and Dave have given you.
As suggested by Andrea's post, many WWII veterans recorded their discharge papers in a public repository. (Actually, the DD214 method of reporting separation was not begun unitl after WWII. A WWII era vet would have an "Honorable Discharge" to document separation.)
Kansas has a system of county courthouses. Colby is in Thomas County. If he returned there after the war, and recorded his discharge, it may be in the county records. Here are two web pages with info that should help you pursue that possibility.
As Andrea indicated, if he received Dept of Veterans Affairs (VA) benefits (to which he would have been entitled because of his service-connected wounds), or if he even APPLIED for benefits, they should have a record of him. If he is on record with them, they may, indeed, be able to help you. The VA national number is 1-800-827-1000. Also, you may have a "nearest VA regional office" in your area. The VA web address, with other info, plus a list of facilities, is http://www.va.govhttp://www.va.gov
Hope this supplementary info is helpful. Good luck.