What you'll need:
Pre-cut rectangles of the Primary and Secondary colors
12" x 18" white paper
Glue stick, pencil and scissors
Scraps of warm and cool colors (I have these separated into 2 boxes)
Small square of gray paper
small plastic dish or lid for tracing
Using a poster or other visual aid, discuss the color wheel and how/why colors are arranged. Having worked with colors the whole year, most kids are very familiar with the formulas for making secondary colors.
Place the primary colored rectangles on the student's desks and show how to cut into a petal. Glue the three petals onto a piece of white paper with the yellow petal pointing to the top.
Repeat steps for creating petals for the secondary colors.
This is the fun part. I tell my students they are going on a treasure hunt for colors to place in between their petals. I fill two boxes with cool color scraps (greens, blues, painted paper scraps, etc.) and one warm color box. The children are responsible for searching through the box to find the perfect red-orange or blue-green. If they are having trouble understanding this concept (which some of my Kinders were) then we brought over their flower to the scrap box and tried out different scraps.
Using a small round container, trace a circle from the gray paper and place in the center. Then, if you have time, ask the children to make stems and leaves.