Such a great thread. It's taken me a while to respond because I'm still pondering.
I don't think I get bored with color with easily. I can only think of two big changes I've made to my color palette, in my whole life: 1) my sophomore year of high school when I decided I could wear pink and still be a tomboy (I'd literally never worn a drop of pink until I was 15!) and 2) a slow shift away from browns and tans over the past decade or so. I'd just always assumed one must have some brown and tan in one's closet, because they're such "practical" colors, but then I realized that they are not happy colors for me and they were generating a fair amount of frustration because they didn't play nicely with the colors I do love. So, in with pink, out with brown, but other than that my colors have pretty much stayed the same.
I think I'm somewhat stodgy about silhouettes, too. Like Rachy, I demand practicality. No extended sleeves for me. I did bellbottoms in middle school, when it was cool to walk all over your hems and get them nice and shredded -- not doing flares again any time soon; maybe one dressy pair at some point. I like the idea of oversized, but rarely love it on me. I only do bodycon for certain types of gear (bike shorts, running tights), never for town clothes. I pretty much live in tailored fits with a dose of fluid -- and in really hot weather, fluid fits with a dose of tailored. It doesn't take a lot of change for me to feel like I'm wearing something new. A turtleneck sweater with bootcut jeans is, to me, a world apart from a v-neck sweater with boyfriend jeans -- but it's the same formula. I can take the same dress, pair it with flats or with tall boots, and feel like two different people.
Like Jenn and others, I also rely on layers for variety: I like sweaters, sweater vests, cardigans, blazers, jackets, hoodies, puffers, thick flannel and wool shirt-jacs. Scarves, hats, arm- and leg-warmers. Are fuzzy earmuffs coming back as a trend anytime soon? I definitely feel like my cold-weather wardrobe has more variety than my hot-weather wardrobe. I need to start collecting sun hats and linen scarves, I guess.
The only thing I get bored with is my hair. Color change doesn't do it for me though -- it's gotta be silhouette change. I love drastic haircuts.