We used Dick Blick liquid watercolors
and a couple of colors mixed from diluted acrylic craft paint.
Since leaf shapes are a little tricky and this is the beginning of 4 year old preschool and we haven't drawn together yet, I created a couple of leaf shape tracers to help us get started. I'm not a huge fan of tracers but I also wanted them to be successful and feel great about their first art experience of the year. Later in the year we will do this project and it will be all their work without tracers!
After they traced the outline
( tracers that you draw inside of are so much easier than tracing around the outside of a shape.) they drew the veins on the leaves. This is where the art starts to reflect their personalities :) Some are very evenly spaced, some drew one or two lines and others drew tons of veins on the leaf.
This is a Sharpie resist technique. The Sharpies won't run when we start watercoloring. The paper is a heavyweight but reasonably priced watercolor paper from Hobby Lobby.
It's still Summer-y weather in Atlanta but we are looking ahead to a colorful fall.