| | Colby, KS | Lamar, CO | United States |
| Population | 5,434 | 7,636 | 329,725,481 |
| Female Population | 50.3% | 47.6% | 50.5% |
| Male Population | 49.7% | 52.4% | 49.5% |
| Median Age | 32.9 | 35.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 5,416 | 7,940 | 309,327,143 |
| Population - 2000 | 5,450 | 8,869 | 285,036,114 |
| Population - 1990 | 5,396 | 8,343 | 251,960,433 |
| Pop. 2000 to Now | -2.5% | -13.9% | 15.6% |
| Pop. 1990 to Now | -1.5% | -8.4% | 30.8% |
| space4 | | | |
| Population Density | 1,465.9 | 1,472.1 | 93.4 |
| Land Area | 3.7 | 5.2 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Colby, KS | Lamar, CO | United States |
| Age 0 to 4 | 6.3% | 7.3% | 5.9% |
| Age 5 to 9 | 7.3% | 8.4% | 6.1% |
| Age 10 to 14 | 7.4% | 5.7% | 6.6% |
| Age 15 to 17 | 3.2% | 3.6% | 3.9% |
| Age 18 to 20 | 7.9% | 7.9% | 4.0% |
| Age 21 to 24 | 6.7% | 4.6% | 5.2% |
| Age 25 to 34 | 13.7% | 12.0% | 13.8% |
| Age 35 to 44 | 8.2% | 10.3% | 12.9% |
| Age 45 to 54 | 9.8% | 11.4% | 12.6% |
| Age 55 to 59 | 4.6% | 8.2% | 6.7% |
| Age 60 to 64 | 8.8% | 6.2% | 6.3% |
| Age 65 to 74 | 7.5% | 9.7% | 9.6% |
| Age 75 to 84 | 4.8% | 3.2% | 4.5% |
| Age 85 and over | 3.8% | 1.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Colby, KS | Lamar, CO | United States |
| White | 88.6% | 54.6% | 59.4% |
| Black | 0.7% | 1.4% | 12.2% |
| Asian | 1.6% | 0.6% | 5.6% |
| Native American | 0.0% | 0.7% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.5% | 0.0% | 0.4% |
| Two or More Races | 0.4% | 1.9% | 3.2% |
| Hispanic | 8.2% | 40.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Colby, KS | Lamar, CO | United States |
| Married Population | 52.1% | 45.8% | 49.8% |
| Currently Married | 51.6% | 45.1% | 48.0% |
| Married but Separated | 0.4% | 0.7% | 1.8% |
| Single Population | 47.9% | 54.2% | 50.2% |
| Never Married | 33.9% | 34.8% | 33.8% |
| Divorced | 10.5% | 13.6% | 10.8% |
| Widowed | 3.6% | 5.8% | 5.6% |
| space5 | | | |
| Household Size | 2.35 | 2.67 | 2.60 |
| Households | 2,146 | 2,744 | 124,010,992 |
| Family Households | 1,259 | 1,741 | 80,755,759 |
| Married couple, w/children | 37.4% | 36.3% | 30.5% |
| Married couple, no children | 43.5% | 36.9% | 42.9% |
| Non Family Households | 887 | 1,003 | 43,255,233 |
| Single householder, w/children | 8.3% | 19.8% | 15.8% |
| Single householder, no children | 10.8% | 7.0% | 10.8% |