Okay, how about this: let's assume a new player solves the series in the intended order. A rating system for a variety of attributes would be more accurate. And I'd suggest ratings out of 10 instead of 100. For example:
Blue Extreme
Dexterity 4/10
Difficulty of new concepts/tricks introduced in this puzzle 6/10
Green Extreme
Dexterity 6/10
Difficulty of new concepts/tricks introduced in this puzzle 3/10
Bronze Extreme
Dexterity 7/10
Difficulty of new concepts/tricks introduced in this puzzle 8/10
I haven't solved Silver or Gold, so I'm unqualified to comment. Heck, I haven't even finished Bronze, but my rating is based on what I've done so far.
Orange Extreme
Dexterity 8/10
Difficulty of new concepts/tricks introduced in this puzzle 9/10
Lime Extreme
Dexterity 9/10
Difficulty of new concepts/tricks introduced in this puzzle 9/10
Noticed I've emphasized the word new. I don't count the
Spoiler:
There's my idea. Have at it.