Posted on: 2022-01-06 19:42:48 UTC
I believe I know just enough to answer this question!
So, sable is considered a "color," and the rule is you can't have another color on top of it. However, you can have a metal or a fur, and you can also sort of cheat by saying your book is "proper," meaning "the color it naturally has," e.g. Sable, a book proper. Depending on the color of the book, though, it might not show up very well (which is one reason the rule of "no color on color, no metal on metal" exists). Sable, a book open [argent/proper] might work well.
As for the second question, I don't see why not, provided your character lives in a society that does conscription and has the wherewithal to survive becoming a deserter. I can't imagine an evil army would take kindly to deserters.