Colo is located at the intersection of the historic Lincoln Highway and the Jefferson Highway. The intersection is marked by the historic complex of Reed/Niland Corner, which includes a museum/diner, vintage gas station, and small park.
For modern-day travelers, Colo lies at the intersection of U.S. Highway 30 (halfway between Ames and Marshalltown) and U.S. Highway 65 (halfway between Des Moines and Iowa Falls). Colo lies also along the cross country line of the Union Pacific railroad.
Colo's most popular attraction is Hickory Grove Park, Story County's largest recreational, fishing, and swimming area (445 acres, dominated by a 98 acre lake). Just east of town, along the Lincoln Highway, lies Colo Marsh, which drains into the Iowa River just east of Marshalltown.
According to the United States Census Bureau, the city has a total area of 0.8 square miles (2.0 km²), all of it land.
There were 339 households out of which 33.6% had children under the age of 18 living with them, 64.3% were married couples living together, 5.9% had a female householder with no husband present, and 26.8% were non-families. 22.1% of all households were made up of individuals and 11.5% had someone living alone who was 65 years of age or older. The average household size was 2.56 and the average family size was 3.02.
In the city the population was spread out with 27.6% under the age of 18, 7.8% from 18 to 24, 30.5% from 25 to 44, 17.5% from 45 to 64, and 16.5% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 98.2 males. For every 100 females age 18 and over, there were 96.9 males.
The median income for a household in the city was $41,711, and the median income for a family was $48,438. Males had a median income of $33,500 versus $24,091 for females. The per capita income for the city was $19,173. About 2.8% of families and 5.6% of the population were below the poverty line, including 3.1% of those under age 18 and 8.2% of those age 65 or over.