I think mittens are a great way to introduce yourself to colorwork. They are quick enough to knit that you can spend some time playing around with the technique, and you have two to practice on before your project is finished. It's also rare that a mitten is too 'daunting' for any level of knitter -- even one with a complicated colorwork pattern is easily mastered. I pulled a few of my favorite mittens from Ravelry and have separated them into skill categories with color recommendations!
Beginning Colorwork: you may know how to knit a mitten up and down, and knit in the round like a pro, but maybe it's your first time trying stranded knitting. Something that offers a little more variation than a typical stripe is just what you need! Mittens like Mandy Powers' Ziggity Mittens work up well in Malabrigo Worsted on size 3 needles. Though this gauge would be hard on your hands with a plied yarn, the buttery softness of singles makes it easy to knit a bit tighter. With a cute picot edge, it gives you a chance to try new techniques with ones you might be more familiar with. If you're looking for something slightly more challenging for your first time out, try the similar Herringbone Mittens with Poms by Elli Stubenrauch. Many people have already knit this pattern in Worsted -- including Ravelry user Amyldubya, whose lovely mittens are pictured.
Intermediate Colorwork: If you've already tried colorwork once or twice, maybe it's time for you to try one of the more complex geometric patterns, or add a third color into the equation. I am of the opinion that the more geometric or repetitive the pattern, the more intuitively your mind will complete it as you knit, which means that you will be able to tell exactly where you are without having to count every stitch of every row, should you use your place.
Some excellent patterns that meet this criteria are Diamonds Are Forever, by Nanette Blanchard. These mittens offer an opportunity to play with color and add more colors to your stranded knitting. The cuff, which contains an organic shape, gives beautiful contrast to the mainly-geometric patterning of the mitten's body. Another great mitten pattern at this level is the End of May pattern by Mandy Powers. This pattern looks complicated - it has different charts for the front and back, and the mitten is lined. But if you're willing to give it a chance, the simple two-color pattern is repeated and actually more intuitive than it seems. The lovely mittens (not in Malabrigo) pictured are by one of our favorite bloggers, Alice Kathryn of Kathryn Ivy.
Advanced Colorwork: It's hard to qualify any part of knitting 'advanced'. Most techniques are easily mastered with some amount of dedication. For the advanced colorwork category, I chose patterns that I felt were beautiful and time-consuming -- with colors changing in almost every stitch, these are not colorwork patterns that you can breeze through while watching television, or forget which row you are on and pick it up easily without counting later. But they yield beautiful results, and their complexity allows for endless applications of color.
Midnight Sun by Randy K. is a pattern with alternating background colors, the potential to alternate foreground colors, a colorwork cuff (which could easily be omitted if you don't like the bell shape of it), and a complicated, large-motif pattern. It would be lovely to see these mittens worked up in rich monochromatic background color gradation (think, Water-Green, Sapphire Green, Verde Esperanza and Cypress) with a bright foreground in a complement, like Vermilion or Ravelry Red. Equally lovely could be a cuff in a solid color, like Marine, choosing parts of the motif to highlight in the same color, making the background solid (if using Marine, perhaps a color like Periwinkle) and adding another cool bordering color, like Fuscia, for interest and 'pop'.
Another lovely pattern with unlimited possiblity is the Hiroshige Mitten pattern by Hanneke Sieben. With a lovely bird motif and detailed cuffs, hems, changing background colorwork and complex foreground, these mittens will be masterpieces as soon as you get them off the needles. Some particularly striking color combinations? Try Burgundy in the foreground, and back it with Polar Morn and Pearl Ten, or go with a more colorful background with Pearl or Natural , backing it on Paris Night with a dramatic Cinnabar harvest moon.
Choosing Colors: For colorwork, color is obviously everything. Take a moment to study a color wheel, and then think about what is across or next to each other on the wheel. Contrast happens with variation in intensity - light and dark, as well as complementary and hue (the actual pigment) variation. Excellent colorwork will have both in harmonious balance. It's fun to play around with color charts and combinations -- draw inspiration from places you love, or blogs you frequent, like The Color Collective, which reveals new and interesting color combinations every day.