Add one more ColorMap

[aymanhab]

This matches with Book figure(s), use by setting preference "Muscle Color Scheme" to "Book"

Fixes issue #

Brief summary of changes

One more option for muscle coloring

Testing I've completed

Loaded states files from existing examples and got colors that match Tom's

CHANGELOG.md (choose one)

• no need to update because new option, hidden for now

[chrisdembia]

I'm not sure users will know what "Book" means. Are there other descriptors you and @tkuchida have been using to describe this color scheme?

[aymanhab]

That's a good point @chrisdembia I wasn't planning on publishing this to users, but rather make it available internally to @tkuchida to tweak a little more or use for figures. If we reach a consensus we can document.

[tkuchida]

I've already made the changes locally and don't plan on using this feature.

[aymanhab]

Thanks @tkuchida I will not merge this PR then until there's a specific need. I'll leave it open for potential future use and to show users what it takes to add a new ColorMap for muscles.