My 1st graders learned about the pop artist Jim Dine and especially his paintings/prints of tools. We talked about how he used contour lines (outlines) and often shaded around his tools for a shadowy effect.
We looked at REAL tools and then they had the option to draw freely or trace the tools. We outlined them with black crayon and then shaded around them. Finally, students painted their backgrounds with colors of their own choosing.
I just love how this one below used only black watercolor and added grungy lines/splatters. I can tell he really observed Jim Dine's work and got inspiration from it! I also love that he restricted his palette all on his own - 1st graders don't often naturally do this!
Oh! And an unexpected tie into their math curriculum! Their teacher told me it went perfectly as they were currently tracing objects in math and calculating the area! Brilliant!
And another limited palette painting below: