Take your picture

Click the pencil in the corner to open the colors

Click the color and drag down to the bottom for black

Click and drag all the way to the left for white

Click and drag all the way to the left, and down for gray

To make colors lighter, when you drag, keep the main color (ex. Blue), and drag over to the white

You can also keep the color and drag down to grey/black to darken it

I hope this helped(: