Robin Williams' "The Non-designer's Design Book" is a must-read for anyone who needs to prepare material for publication (including software UI), and includes a chapter on colour:
The principle of design are not difficult to learn but they're not always easy to put into practice and that's why it's considered an art rather than a skill. Certainly WPF/Silverlight is a designers dream as far as desktop UI is concerned since it's VERY flexible so you'll find few restrictions on what is possible when compared to other technologies. Blend works well with them too and it's not that tough to learn.
To start learning design as a developer, i'd suggest you take in as much material as possible and pratice,..a LOT. Read design blogs like the ones here and read plenty of books. Some good starter books are The Non Designers Design Book, The Design Of Everyday Things and Don't Make Me Think. I know they all really help when i started to look into UI and interaction design.
Hope that helps.
This won't help you come up with original designs, but might be helpful nonetheless.
The single most significant increase in my understanding of CSS layout came with using Firebug's "inspect" feature. Being able to see an element's computed style in the "style" tab and its padding/margin/offset in the "layout" tab were (and still are) a tremendous asset.
As far as learning to design as a developer, Robin Williams' Non-Designer's Design Book is a great starting point. I own a copy and definitely would recommend it to any developer who wants to understand design in less abstract terms.
i think it's a rather popular question here:
And if you haven't read it yet, do read Don't make me think and Non designer's design book for good page layout design.
To improve just look around at existing sites. In addition to the books already suggested, you might like to have a look at Robin Williams's excellent book "The Non-designers Design Book" (sanitised Amazon link)
Have a look at what's possible in visual design by taking a look at the various submissions over at The Zen Garden as well.
UI design is definitely an art though, like pointers in C, some people get it and some people don't.
But at least we can have a chuckle at their attempts. BTW Thanks OK/Cancel for a funny comic and thanks Joel for putting it in your book "The Best Software Writing I" (sanitised Amazon link).
I started looking into useful material to help improve my non-design skills, because well... they are non-existent.
I started with Twitter Bootstrap but I don't think it is the way forward if you want to learn design the proper way. I recently bought this book: The Non-Designer's Design Book (http://www.amazon.com/Non-Designers-Design-Book-The-Edition/...) and would warmly recommend it to anyone who wants to put one foot or their whole body into the design world.
I now try to spend more time analyzing the design of websites, brochures, menus, etc. It is very fun and I believe it is my observing and analyzing other peoples' work (mistakes included), then practising, that you can improve your eye(s) for design.
It was written without the web in mind. It's mostly about typography and spacing for posters, business cards, flyers, etc. But it translates suprisingly well to web design.