Michigan Wolverines Helmet Design?

Is there any meaning/symbolism behind the helmet design of the Michigan Wolverines?

Helmets are usually blank w/ midline strip, have a letter or symbol that represent the team name or university, but I don't get the yellow on blue design of Mighigan's helmet. Can you help me understand?
Update: Thanks for the answers.

I found an interesting website that also helped me answer my question.

http://www.umich.edu/~bhl/helmet/mhelmet...
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