Hi Alex, I've observed this in various populations of Egernia spp. in the Central Tablelands of NSW.
Interestingly, as recently as last week, the larger "western" form of Egernia cunninghami were already becoming paler (as this form tends to do in summer), with the warm spell that the region had been experiencing lately. As you probably heard, last Friday the Blue Mountains/Central Tablelands (and beyond) experienced a freakish cold snap with rarely seen dumps of snow. I explored some of the snow covered areas to see what effects the change had on flora and fauna. Yesterday was still cool (as was the weekend) and I noticed that the Egernia spp.* seemed to be a shade darker. I wasn't sure if this was due to the animals being damp from the associated precipitation, so I checked again after they'd been basking (and therefore they'd dried out) and they still appeared to be a bit darker. I was surprised that such a relatively rapid change in tone can occur in response to such a severe weather event; especially in a group of lizards not known for colour change.
* i.e Egernia cunninghami and E. saxatilis intermedia.