I recommend checking out 'universal principles of design' and o'reillys 'designing web navigation'. These two will give you a good overview of different aspects of design while helping you understand how design works on the web. I think that in starting to learn about all of this, it would be advantageous to approach things from an 'information' angle. That is, web design is information first and aesthetics second.
Beyond that 'A Designer's Research Manual' is well worth reading.
And for colors check out http://www.colourlovers.com
