It seems from the history that your seven year old son has fever
along with cold and cough indicating upper respiratory tract
of the eyes is commonly seen in febrile conditions like fever because of reflex hyperemia
. It is only transient and it will decrease with treatment for fever.
Since as from your history there is no discharge or watering from the eyes, which indicate conjunctivitis
, no need to worry about the redness of the eyes. The condition will resolve with treatment of fever.
If symptoms like watering, discharge are present along with redness of eyes, you need to consult eye doctor.