It's alright yeah,
In my sketches i dont colour them in, i coloured a ttar that i drew once and it toally ruined it,
So you you use sketch pencils?
If you do, Get the lightest pencil and sketch really lightly so you can rub out easily if theres a mistake, then use the next lightest pencil for the darker bits, then when your happy with everything, go over everythin in the darker pencil, if you think it will look better, colour it in but lightly so it doesnt ruin it.
Good work though.