Up until recently i have used one UV tube and one basking light in each vivarium. After reading around i have just upgraded my new vivarium to containing one UV tube, two basking lights (one 60W and one 40W - needed an extra smaller one as the temperature range was not sufficient) and one daylight bulb (high CRI, >85 and Kelvin temperature, 6000K). This extra bulb brings out the colours immensely and the geckos seem a lot more active.
When i first started with phelsumas i found that there was a very small amount of information regarding lighting for them. I still find it confusing. Ideally i think it would be better to have more than one UV tube and one daylight tube but due to practical reasons (in my circumstances) this is not possible.
I am glad people ask questions regarding the lighting as i am shocked when i see some people caring for phelsuma with just a basking light and a heat mat on the bottom of the vivarium!
hope this helps
julie