Dear L.,
When my brother went to first grade back in 1950, he would color everything with his black crayon. Even when the teacher would take the time to hand him the correct color to use, he'd change to the black crayon. The teacher tried to tell my parents that he had a learning disability and that he was slow. The teacher also thought he might be depressed because he used black crayon for everything.
As it turned out, my brother was extremely intelligent. He just liked the black crayon. There was no changing his mind, because he was a very stubborn, independent person. He thought his teacher was funny, and he enjoyed getting her upset. He went on in life to be an engineer. He even designed the hydraulics for the Jaws ride at Universal Studios in Orlando, Florida.
Think your daughter might be having some fun with you? Try saying something like this with a smile on your face: "Are you teasing me?" Try it each time she tells you the wrong color. It almost sounds like she just likes purple and green,and wants to get a reaction when she uses them all the time. I'd play along and see if she tells you the correct color if you use the wrong color sometimes.
Kids develop a sense of humor very early. May be that this is what your daughter is doing with you. Wouldn't that be neat!
Sincerely, M.