Hi,
I don't think its any cause for alarm. Most people see floating colors after turning off the lights. Try staring at a light for a few seconds and then closing your eyes. You generally see colors. Its the leftover imprint of the light and usually resolves in a matter of minutes.
Hi,
There is a possibility that this could be migraine since she has headaches as well.
Other possibility could be synesthesia in which people see colors. But there is very limited information on this condition. The part of the brain associated with color perception was found to be unusually active in these patients.
Take care!