From Colorados division of wildlife's web site.
A primary tool used in the management of Colorado’s big game animals is a limit or quota on the number of licenses issued in most game management units (GMUs). When applying for a limited license, a preference point in awarded when an individual is unsuccessful in drawing their first-choice hunt code. Preference points provide a mathematical advantage when applied to future drawings.
If you hunt with your cow tag you still keep your preference point.
If you ask for a refund for your cow tagit must be done before your season starts. You still keep your preference point.
http://wildlife.state.co.us/NR/rdonlyres/75A4E687-F7B3-496F-BF49-4D60AC7F37CE/0/DOWLicRefund.pdf