Green coolant in a '92 Camry

My friend recently noticed her car was low
on coolant, so she went to the gas station
and bought the only one there, some
(presumably) universal green coolant. I
know that Toyotas are supposed to have
brand specific red/pink coolant, but I am
unsure of the importance of that. She
cannot afford to take it to a shop so I was
wondering if I should flush it tonight (it has
to be moved again tomorrow) or if it will be
okay to drive for a few months with green
coolant until she can get it fixed later? She
says the reserve tank looked empty and
the car was over heating, so will that small
amount of the other coolant mixing with it
cause any trouble? Thank you!