This is probably my favorite medium. Good colored pencils however can get very pricey. There are many low-quality sets you can buy if you're just starting out, but if you think you're going to do this a lot, I'd consider investing in a high-quality set as the colors are just so much better. Colored pencils are easy to use and to blend colors together. Gradients are effortless with this medium. There are two styles with these, one just lays the colors down, slightly overlapping two colors to create a gradient.  The other uses a burnisher, which is just a colorless pencil to push the color into the paper. This technique makes the colors a little more vibrant, helps obscure the paper color and helps with blending the colors. These work well on most papers, but I prefer a lightweight Bristol vellum best.

If you love vibrant colors, markers are the way to go. I find them very bright and fun to use, but a little unforgiving. It's much harder to get good blends between colors with these but, it is possible with practice. This is also one of the cheapest mediums to start with. There are a lot of decent brands out there with a wide variety of colors in most sets. There is no erasing them though, if you don't have a steady hand, pics can get sloppy real fast. If you do though you can't beat them. I love to use these on either marker specific paper or a heavy cardstock.

I recently started working with these and they are a lot of fun. If you prefer the look of pastels to vibrant colors, this medium might be for you. They are a little messy but it's minimal. The trick is to always put your hand on a tissue, so it doesn't get all over your hand and then mess up your picture with chalk transfer. To blend it and push it into the paper a bit you can use a tortillon, Q-Tip's or what I discovered that works great was a silicon clay shaper, just a rounded one with the pointy tip. This medium works well on most papers.