I did a bit more searching on this topic, and here's what I found out with whether a state uses enhanced mile markers or not, at least in urban areas, and which color and interval:
Blue enhanced mile markers:
- Indiana (0.1 or 0.2)
- Kansas (0.2)
- Kentucky (0.1 or 0.2)
- Ohio (0.1 or 0.2)
- Tennessee (0.2)
- Wisconsin (0.2)
Green enhanced mile markers:
- Connecticut (0.2)
- Florida (0.2)
- Georgia (0.2)
- Illinois (0.2 or 0.25)
- Iowa (0.2)
- Louisiana (0.2)
- Massachusetts (0.2)
- Michigan (0.2)
- Minnesota (0.1)
- Mississippi (0.2)
- Missouri (0.2)
- Nebraska (0.1)
- Nevada (1)
- New Hampshire (0.2)
- New Jersey (0.1 or 0.2)
- New Mexico (1)
- New York (0.1 or 0.2)
- North Carolina (0.1, 0.2 or 0.5)
- Oklahoma (0.5)
- Oregon (0.5, limited use)
- Pennsylvania (0.1)
- Rhode Island (0.2)
- Utah (0.1, limited use)
Some form of fractional or decimal mile markers:
- Colorado (0.1 or 0.2)
- Delaware (0.5)
- Maryland (0.5)
- Vermont (0.2)
- West Virginia (0.2)
Standard integer mile markers only:
- Alabama
- Alaska
- Arizona
- Arkansas
- California (uses white county-based Postmile markers)
- Hawaii
- Idaho
- Maine
- North Dakota
- South Carolina
- South Dakota
- Texas
- Virginia
- Washington
- Wyoming
I'm kind of surprised about some of the states that don't use enhanced mile markers, or at least subdivide their mile markers, like CA, TX, VA or WA, as well as OR and UT outside of one freeway each. They have some large cities that could probably benefit from 0.1 or 0.2 mile markers for roadside assistance.