I think color theory is great in lower grades-with 3-4 I do the color
wheel to the third level by having them mix and create a color wheel
then paint hot air balloons using the color wheel
In 5-6 I am teaching complimentary, analogous and optical color mixing
via Seurat and pointillism. They love looking at a color then closing
their eyes and looking at white paper and seeing "a new color", also how
two primary colors next to each other create another (blue and yellow
close = green from afar).
I think its like magic and they really get a kick out of it. Even my 1-2
graders enjoy learning primary and secondary colors.