Skillwheel (mod: Moonst@r)

The icon is clearly visible. There's nothing to examine, and you won't mistake the correct button.
Can you show an example of a "classic-style" one? I don't quite understand.

I won't make a mistake; I can simply guess based on the color that brown represents dwarves, but if someone isn't very familiar with the game and doesn't see very well, they might get confused (I experienced this while playing with someone), because a brown head on a brown background looks like an empty space compared to the others. This is especially noticeable when you're looking at it from the corner of your eye and the panel is out of focus, but these are just my personal preferences.

I can't show an example of a button right now; there was one in a mod for the undead raising table, and it had a green button with a yellow skull.