When it come to buying and using markers, I have tried so many brands. I have now, mostly settled on two brands: promarker and copic. I also have spectrum, which are good, and stampin' up, which to be honest I am not that fond of. I have heard really good things about the Tim Holtz distress markers though I have yet to try them.
Copic colours are created with codes to help the user pick colours for blending. However, not many people understand the codes.
The letter is to tell you what colour family it belongs to:
B: blue E: earth G: green R: red V: violet Y: yellow
BG: blue/green BV: blue violet RV: red/violet YG: yellow/green YR: yellow/red
The first number tells us the saturation of the colour (0-9); the higher the number the greater amount of grey that has been mixed in.
The second number tell us the brightness/shade (0-9); the higher the number the darker the tone.
Link to Copic Colour Wheel: http://www.copicmarker.com/wp-content/uploads/2011/02/color_wheel_2011.pdf
Good luck and have fun.