The clothes: Unless you find a really amazing print that incorporates both these two shades, stick to simple shapes in solid colors. Since yellow and grey are already so drastically different, the outfit looks forced if there's too much going on.
The accessories: This is where you get to experiment: try a pattern! Wear a statement necklace! Just be mindful that your bag, jewelry and shoes all work together.
The clothes: This particular mix is all about juxtaposition, so the girlier the pink and grungier the green, the better. But limit yourself to two major pieces so the effect's not diluted.
The accessories: Clean and crisp black or white, maybe a little bit of understated jewelry. Don't overdo it.
The clothes: To keep these three vibrant shades from competing for attention, pick one hue (here it's blue) to dominate the outfit. That downplays the other colors, and creates a cohesive look.
The accessories: Matte black is nearly impossible to mess up, but any sort of metallic will also work—especially for the evening. Tans, creams and "earth tones" in general, however, should be avoided.
The clothes: The key to making mixed pastels seem more sophisticated than trendy is to create extra contrast between the two hues. Here's how: use one shade for the main outfit (a dress is the easiest way to accomplish this, but a top with white pants would work, too) and save the other for accessories.
The accessories: Besides a few pieces in your second, non-clothing color, incorporate any variety of silver, gold or peach. Don't do black or brown, though—either one will look clunky.
The clothes: Honestly, this one's awfully hard to get wrong. So long as you stick with a fairly even mix of the two shades (aim for half and half) it's going to be awesome.
The accessories: Also white and cream. Any other color—neutral, bright or otherwise—ruins the understated, subtle effect that makes this look so great.
The clothes: Whether it's a cardigan over a dress, a button-down tucked into a fit-and-flare skirt or slacks and a sweater, any combination of two pieces will work. The most important thing is that the bold shades balance each other out.
The accessories: Black or white or both—colorless prints help break up all the big areas of brightness.
The clothes: Just a bit of burnt orange goes a very long way, so you honestly only need it on one item of clothing. If skirts aren't your thing, skip this particular look and try black cigarette pants with a chunky, rust-colored sweater instead.
The accessories: Black, obviously, but also one other neutral (beige, grey and white are all excellent choices) so thing don't get too dark. The best way to work in some color is with lipstick—we'd go deep burgundy!
The clothes: Because there's something inherently sporty about this mash-up, it's best suited to streamlined, athletic shapes.
The accessories: Adding in more of either color comes off too matchy-matchy, so work in some dark shades of blue. It fits in the outfit without feeling forced.
The clothes: If you don't have a neutral piece as a buffer (like jeans or a black skirt), it's best to let just one hue dominate the ensemble. Use your accessories to add the other.
The accessories: Keep the second shade on just one item, and stick with black and gold for everything else. Over-coordinating the colors can come off as stiff.
The clothes: Although you could definitely nail this pairing with a salmon pullover and wideleg tan pants, working from the waist up is much easier. All you need a coordinating sweater and jacket!
The accessories: Leopard print accents are a nice complement to all the warm tones you've got going on, but don't go overboard. Just a small touch will get the job done.