Q&A for How to Draw a Ninja

Sure. Add female eyes and a ponytail in the back.

Of course, it's up to you! Usually the eyes and lips are what define the character's gender, so as long you can tell the gender clearly by the eyes, any hair is fine. Consider drawing long eyelashes to make it more obvious.

The easiest way, would be to draw the robot first. Then you could draw the ninja clothes. If the robot is gray, white would be a good clothing color, as it doesn't contrast too much with the robot color, but it doesn't blend in too much either. For instance, you would start out with a curved rectangle for the robot's head, and then add in a face. After, just choose a good pose, and draw the clothes. The easiest way is to draw it similar to a robe, with slightly too big sleeves.

Draw the simple shapes first. For instance, the head would be a circle. After drawing the shapes first, start adding detail.