Child couldn't identify colors correctly, for a brief period

[geetha_boppana]

Hi,
My 6 year old suddenly couldn't identify the colors correctly. she first said that i looked gray and black to her, then i started showing her individual colors and she messed up everytime. she was saying orange for yellow ,blue for green and vice versa. (BTW, she is very good with colors. she always paints). we immediately took her to the eye doctor and he examined her and found out that she has astigmatism. He also made her read the color blindness chart. she did very well. (i don't think, astigmatism has anything to do with color recognition) . while we were waiting in the doctor's office(2-3 hours passed after this started) she started to recognise the colors correctly (just like that). And now she is fine. the doctor thinks she was just playing with us to get glasses. but i can't agree with him. she is not old enough to make a plan like this. Please Help! Is it serious??
P.S she fell the day before and got hurt on the back of her head. but she said it didn't hurt much. I am not sure if this has anything to do with what happened. Thank you in advance