holy shEEt!!! She sounds like a prime candidate for BRIDZILLA! Shower & wedding registeries are great tools to let people know the kinds of things you need/want. HOWEVER, it is not mandatory to provide a gift soley off a registery. It's also in MAJOR poor taste for her not to have selected registery items that cover ALL price ranges. I have heard of theme weddings and I've heard of people let'n their guests know whether it's formal, semi-formal or casual but down to a specific color *shrugs* seems over board to me (but then again, I wanted 2 get married on cruise ship while drink'n champaigne in the jacuzzi so the few peeps I invited the attire requirement would have been swim suits! lol)
ANYWHO....
Since you're a co-worker w/no intimate relations, I wouldn't feel obligated to give a gift or attend either event.
If you want to attend her shower, give what you can afford or a gift certificate to where ever she's registered works too :) OR since your place of business is hosting the shower (which is kinda wierd to me ... usually a wedding shower is hosted by the maid of honor and/or the mother of the bride) You could suggest/ask if they'd all pitch in and get her one of her 'choice' gifts. Get a card & have everyone who pitched in sign it. Then when you go to the shower & present it as a gift from 'the office', everyone can feel good :)
It's been my experience that people who invite everyone in the world don't really expect them to attend but hope they'll get a gift anyways :) (key word - hope)