I checked out the Grand Cathedral map and with all those different elevation labels it got quite confusing but after a moment or two I got the hang of it.
For player's I think it would be the best if there were no labels and the DM just told them the heights when they were useful (bull rushes e.t.c.) but for the DM that would be hectic.
Now about the color elevation system that would have to be quite discreet as not to turn the map into a circus.
So I think I would go with the colored elevation system if you could make it look nice, but if not then comes the labels but for sure don't do it without any elevations at all.