When you read/hear the phrase "fluffy sanguine velvet" does what happens to me, happen to you? I know sanguine is about blood and that's why it's about humours, but...reflexively it means "confident and helpful fabric" and then I make it to blood-red.
I'd argue in this scenario it might even be worse than using a word that the reader doesn't understand at all. The process of "that doesn't make sense...well, it could make sense...let me double-check so I can be sure..." is more jarring for me than "fuck, I gotta go look this up."
Which disrupts you more as a reader?
(And I'm not going to lie—I judge fanfic writers by their errors and word choice (professionals generally only by word choice, and sometimes I hate their editors, even though I know great editors (Can you imagine editing Delany???).) But I judge them as word-generators, not as people, until we get to the content, not the presentation—THEN IT IS ON (a poor writer whose story I just finished kept apologising for the homophobic words and acts she had to write for her conflict, meanwhile I'm mad at her for twisting decent to complicated characters into moustache-twirling villains to move the story along. What show doesn't come ready made with villains in it? And when you make a canon villain a best friend—fine, you don't know what loose or naval mean, BUT COME ON))
"Sanguine." Merriam-Webster.com. Merriam-Webster, n.d. Web. 7 June 2014. .