Well if your using markers than stop thats the worst item to use. coloured pencils are ok but if you have acces to a computer i suggest coloring them on photoshop.. to get you'r drawing on photoshop you must scan your drawing into a jpg. file. After that you simply open photoshop and and select file (in the top right) then select open, search for the file you saved it under and then start to colour and add shading.