This is a segment from the 'Amphibian Research Centre Care Sheet' in relation to Australia's White Lipped (Giant) Tree Frogs:

'Although giant tree frogs are largely nocternal they shelter during the day in areas exposed to sunlight. It has been observed that in captivity a failure to provide ultra violet light has resulted in stunted and deformed growth'.

'Those that are white or near white when switdhed off and pale blue when on emit light in the right spectrum.'

'Lights should be placed on a timer for at least 6-8 hours a day.'

'Be sure that the cover in not benesth the light fixture as this will stop the necessary UV light from reaching the frogs.'

Please bear in mind that this is for Giant Tree Frogs, not Grey Tree Frogs...I would think (not saying that I'm correct) that it would be a similar principle...