Joeli asked for pointers on subbing colors. Well, that could be a whole book by itself, but maybe I have some short little ideas that fit in a blog post.
Obviously, the first thing is to consider what colors you like and want to wear. Or, if the garment is a gift, what would the recipient love to wear? Think about the overall mood you hope to create with your color choices. Soothing and serene? Flashy and outgoing? Autumnal? Springy?
Let's say, like Joeli, you really like the graphed stitch pattern I used for my vest, but you really don't like my color choices. Say you love blue. Maybe you would choose to do the darker foreground pattern in a dark navy blue. And then look for 3 mid- to light-blues and a creamy white to use for the background. That kind of colorway would result in a very soothing garment. Maybe you make a swatch (or a hat instead of a swatch) and think, "Well, I love blue, but this is putting me to sleep. How do I perk it up just a little?" Maybe you try taking out the white and putting in a pale yellow. Or a vivid yellow. Suddenly your swatch is generating some energy it didn't when it was all blues. And maybe you liked it with less energy, so you go back to white. There's no right or wrong on that. It has to work for you: what will you feel comfortable wearing?
Maybe you like your pallette, but you really want a darker garment. Swap your foreground and background color sets. Now, you're looking at all those rows of navy blue and you want to liven them up, just a bit. Maybe you try subbing out a few rows of the navy with a dark grey with cool undertones. (What does she mean by cool? Looking more like the blue and green side of the color wheel. Warms look more like the red and orange side. Few greys are truly neutral; seeing which way they lean will help you use them to your advantage.) Or even a warm dark grey. How about a smidge of black? Maybe a dark piney green?
I have spent a lot of hours knitting fair isle swatches just for the learning experience. As I said in a previous post, I've read a few books, too. The books help and they give you a useful vocabulary. But they need to be supplemented by trial and error. You can do some of that on your computer in a drawing program. Or with colored pencils or markers on graph paper. This doesn't get the whole picture of the way different yarns show texture or reflect light, but it's a good learning tool.
Last night I was thinking about some guys I knew in college, Nick and Paul. They were both very cerebral. They liked to chat about Nietzsche for fun. Paul grew up in inner-city Detroit. One summer when he was visiting Nick in Boston, they went to the beach. A large wave was coming and Nick yelled, "Paul, a wave is coming! Can you swim?" Paul replied, "Oh sure, I read a book about that." Nick is now a professor in Australia. I'm not sure where Paul is.
In so many aspects of life, there's no substitute for hands-on experience.