The flag of Mesa County can be seen at
https://www.westernslopenow.com. It depicts the Mesa County logo centered
upon it (the inner circle in white, not transparent); the words "MESA COUNTY"
are found above it and the word "COLORADO" is found below the logo, all in a
brush script. The field is blue. Clearly, the logo depicts the county's namesake
(named for its many mesas).