In order of suckiest to 'OMG I love this marker' here are the results!
16. Copic Dual Tip
The Copic markers are on the pricey side, and they go straight through most coloring book paper stock. Plus they smell really strong. Thumbs down.
I know Sharpies are handy, and you almost always have some in the house. BUT, just like their more expensive Copic counterpart, they went straight through the paper and they smell pretty bad. (Unless you like the smell of Sharpies, in which case I say, put the marker down, and go get some fresh air). Thumbs down.
14. Derwent Inktense Pencil
If you use these colored pencils dry, they do a really nice job. They're soft so they cover and blend well. But if you wet them to make them more vibrant, and permanent, they do go through the paper. Not as badly as the Copic or Sharpies, but still....not great.
13. Sharpie Paint Pen
I love paint pens, love them. Except for the Sharpie ones. Now, don't get me wrong, I'm not hating on Sharpies - usually I love them - they're just not great for coloring. The sharpie paint pens have a super fine nib, and seem to be both watery and dry somehow. So they don't cover the paper very well, and they also tend to bleed through. Thumbs down.
12. Y&C Gel Pen
You'll be there for days, head hunched over your coloring book, hump starting to form on your back, just trying to coloring in with these gel pens. The ink isn't free-flowing and the nib is ultra tiny! They might be ok if you have some teeny-tiny detailed spaces to get into, but otherwise I'd avoid them. Thumbs down.
11. Montana Paint Pen
This is a BIG nibbed paint pen. If you got a big area to cover, great. But if you're trying to do the fine detail required in most adult coloring books, forget it. Surprisingly it didn't go through the paper, despite laying down a thick, opaque layer of paint!
10. Liquitex Paint Pen
I love the variety of colors the Liquitex Paint Pens come in, but they can be a little watery and were just starting to go through the page a little if I colored a larger space with them. They are a fairly broad-nibbed pen too, so not great for finer detail.
9. Sharpie Metallic Marker
The metallic Sharpie ink is much more opaque than its colored friends, and doesn't seem to bleed through the paper at all, unless you do some serious scrubbing. Thumbs up. Side note though, it will cover up your black lines. So you either have to be ultra careful, or not mind too much when the shapes start blobbing together.
8. Uni-Ball Metallic Gel Pen
This metallic gel pen is wonderful. The ink practically glides onto the paper, it gives reasonable coverage for a fine nib, and it doesn't bleed through the paper! Thumbs up.
7. Staedtler Tri-Plus Pen
These pens have super fine nibs, but the vibrancy and color range they offer is outstanding, and then won't bleed through your paper either. So I'd definitely recommend them for those more detailed coloring pages. Thumbs up.
6. Uni Posca Paint Pen
I love, love, love this pen. It has a smaller nib than it's Liquitex counterpart (still a little larger than a Sharpie though), and the vibrant paint is super opaque and glides onto the paper. Best of all, it doesn't go through the page! Amazing! Thumbs up!
5. NPW Sketch and Sniff Colored Pencil
For super-cheap colored pencils, these weren't too bad at all. They blended well, weren't too waxy, and best of all they smelled delicious! Thumbs up.
4. Prismacolor Watercolor Pencil
I found the Prismacolor pencils to be a little waxy and hard to blend, which is strange for a watercolor pencil. They're usually super soft. Having said that, you could wet them and blend the color out, and as long as you didn't go crazy with the water, there was no bleed-through. Thumbs up.
3. Derwent Watercolor Pencil
The Derwent pencils are nice and soft, blend and cover well, and you can use a little water to spread them out and make them more even, without them bleeding through the page. Thumbs up.
2. Winsor and Newton Watercolor
Surprisingly the watercolors did really well. They were easy to fill in small spaces with a fine brush, and as long as you didn't get splash-happy and use too much water, they didn't go through the paper! Thumbs up.
1. Faber Castell Pitt Artist Pen
Ooh, ahh. The Faber Castell markers were my favorite. They have a brush tip so you can easily get into the small crevices, as well as block-color larger areas quickly. They come in loads of colors, they don't smell, and unless you are really scrubbing (and in which case I suggest you get a grown-up to show you how to hold your marker correctly) they won't go through the paper. We have a winner folks!
Here's the front and the reverse of my test page. You can see the sharpies and Copic pens went through the worst, followed by the Inkense pencils when wet.