It sounds like they have a way of marking trails by difficulty only. That's a nice feature, but what happens when two trails of the same color cross? Are they still named? How does this get you from A to B without a map?
Example of a map: https://mapy.hiking.sk/?zoom=11&lat=6261583.4553&lon=2274012...
I just don't see the utility that makes this such a great idea.
Bonus point: whole system depends on volunteers who keep markings on all lines.
„Red – long distance and summit trails; you can pretty much walk through the whole country following the red markers
Blue – significant trails
Green – local trails
Yellow – short or connecting trails, shortcuts”
https://mapy.hiking.sk/?zoom=11&lat=6261583.4553&lon=2274012...
It's not perfect, though. Sometimes you'll see a sign pointing diagonally past an electric fence and think that maybe the sign is slightly off and you're supposed to walk along the fence. But actually the path goes across the meadow and the farmer who uses it later decided to erect a fence. Other times the sign is really just slightly off.