hopefully this should help you...
explanation.... first you need to work on your lines... sort out the shape as shown so that it seems to actualy be 3d not a flat thing.... next you need to shade your lines, look at the colours i used compared to what you used.
the colours i used are more interesting because i have switched hues in the shades, you can see the darker shades are more blue where as the lighter shade is more yellow i have done this because yellow is normaly more associated with light and the sun as blue is for night and shadow.
The way to shade your piece is to decide a light source... mine is top left for this and you can see if the light was comeing from the top left the light is where the light should be and the shadow is the opposite side too the light source.
then you can add some final touches... you can AA makeing it smother, add a thick border for style or if you wanted it round instead of square its easy with a simple modification of shapes.
study this and have a go at the whole process yourself useing this as a guide.. try to make the red one.
