Had she seen them in a paper and was this only an after-image?
This is known as an after-image and there are many interesting variations.
When fatigued to red light the after-image on a white surface is blue-green.
Their colors varied in the same manner as the after-image of the sun.
Stimuli earlier than A are no longer represented in the after-image.
The after-image will be found to mix with an objective color in accordance with the principles of color-mixture mentioned above.
A pale blue-violet shadow floated across the page before me, leaving an after-image of pure colour that was indescribable.
Otherwise no particular training of the subject is necessary beyond that needed for the observing of any after-image.
With these eye-movements, the possible appearances are of two classes, according to the localization of the after-image.
What relation the 'constant product' bears to the duration of after-image will be spoken of later.