With devamps, it depends what gen you're doing, but the outlines are never just black. They're always coloured in places, and their two colours are often far apart on a shade scale. They also use the colours to shade the other parts, such as using the lighter blue to shade the silver cross. You also need more dark shading, which can be done with black as you have demonstrated, or with the darker colour. If you reference an old sprite, you'll see better how they used the colours. :] Good attempt, though. :D