Copic Markers have been around for a long time in the architecture and art worlds. They are high quality, long lasting (won't dry out for years and you can store upright or on side), color consistent, non-toxic, acid-free when dry, refillable and come in 334 fabulous colors. They are permanent (color your gems and buttons) but don't cross contaminate – you can't ruin one marker by touching it's tip with another.
They are alcohol-based dye markers, which means a lot of great things. No matter how many times you color over an image, it will not cause the paper to pill. They give smooth results (no more stripes in your colored images!) and the ability to blend.