Naturally I would prefer it if my workplace insisted on suits as it would give me an excuse to go out and stock up :) However, the dress code is Business Casual and not even the CEO wears a suit and tie. I find myself going to work every day in a combination of shirt, smart trousers and wool jumper and I find it dreadfully boring.
If I try to add a splash of colour with a tie I get funny looks for being overdressed but all the same I take a pride like we all do here; any suggestions how I can jazz things up and still look businesslike?
EDIT: Should add we're not allowed to wear jeans and it's winter here; it's not been too cold recently but we get a lot of wind and rain so blazers are pretty much out of the question.
I don't wholly understand the point you make about blazers (I assume you mean all odd jackets by this): you can still wear a jacket under a raincoat. I'd add a couple of good odd jackets to your wardrobe.
It might be that you could go for something other than a shirt too - perhaps a long sleeved polo/collared light wool top might work with a jacket too.
I'd second what Wolf said... try a fine knit rollneck maybe? Especially if you get a blazer to wear it under. What colour knits are you wearing at the moment? That should be an opportunity to add colour, or maybe even some subtle patterns.
Also good shoes & jazzy socks!