If you've posted anything in this most recent post, I thought I'd let you know that it hasn't posted properly. As far as the colouring goes, you just need to work in some light and shadow. Imagine a light source coming from one side, and draw the opposing side in shadow. Just use darker shades of the colours you've already used for now, though as you get more experienced, you can use slightly different hues and saturation to make it more realistic.
I don't think the colouring is a major issue. Yes it needs work, but it will come when you get more comfortable with whatever digital program you use. The line quality however, needs more practice. Try to keep the line steady -which I can't do digitally, I'm like a chimp with a spachula when I try to use a tablet- and vary your line weights.