Flowers

This picture could be created using only the pen tool.  It would not be difficult, but it would definitely require a lot of patience.  First, the actual petals would have to be drawn.  Next, the dotted lines that radiate outwards would be drawn, and the setting changed from a solid line to a dotted line.  The grid view would be helpful, because all of the intricate curves are proportionately spaced out.  In terms of the colors, you would have to open the color palette and then use your mouse to drag the palette down and reveal the large-view spectrum.  From there, it would be easy to experiment with slightly varying shades of green, blue and yellow.