First off, a disclaimer: I'm an earth tones girl. I like subdued colors and you will probably never see me knitting with anything neon. These rules might not apply to you if you like your colors loud, but they're what I try to follow to make knits that I like to wear.
Awhile back, I wrote a post about colorwork knitting patterns for beginners. Once you've got your pattern selected, though, picking out colors can be HARD. And when it's a big project, like a sweater, you don't want to invest all that time and wind up with something you'll never wear. So, here are some tips that will hopefully help you choose colors you love on your next project!
For solid colors, consider your current wardrobe. I know I wear primarily dark green, burgundy, gray, and dark blue. So, when I'm choosing a color for something major, like a sweater, I tend to stay in that color palette rather than knitting something in a color that I will never want to wear.
For colorwork like stripes, stranded work, or brioche, choose colors that contrast with each other. There's no point in knitting with two colors if you can't tell the difference between the two! For stranded work, make sure it's a significant contrast, which will help define the pattern. For stripes you can be a bit more subtle with your contrast because the pattern is predictable. And brioche, honestly, I think can go either way, depending on the look you want.
When your pattern only involves two colors, try choosing a neutral and a pop of color to prevent two strong colors from conflicting with each other. When third, fourth, and fifth colors are involved, they often work well if they are variations of one of the other colors, or a small amount of a coordinating color.
Let's have some visual aides!
My Clarke Pullover that I recently finished! I've got a neutral (gray) and a pop of color (burgundy), all staying within my wardrobe's color palette.
Telja by Jennifer Steingass
In this sweater, the main color blue serves as the color pop while the rest are neutrals and all variations on gray.
Stairsteps Mitts by Stephannie Tallent
No definite neutral in this one, but the dark orange main color is so muted it almost looks brown. So, we'll call it a neutral. The contrasting colors are light orange (a variation of the main color), and then blue serves as the pop of color.
In this little fair isle cardigan I made for my daughter when she was a baby, gray is my main color and neutral while the remaining four colors are all variation of pink, my color pop.
Hope this helps you choose colors that you love on your next project!