That's a different claim. Blue light can interfere with Circadian signalling. Nothing new there, though the issue is under-recognized. What is being claimed

That's a different claim. Blue light can interfere with Circadian signalling. Nothing new there, though the issue is under-recognized. What is being claimed is that blue light is good for staying alert, presumably during the working day. That's more tricky, and would argue that blue-light is reinforcing some aspect of the cycle or has a unique physiological effect. This is, however, unlikely; blue light serves primarily to entrain the clock, i.e. to keep it in period and phase with the daily cycle. Without this light signaling, your clock will 'free run' which is a cycle that is slightly longer than the 24 hour cycle. Crucially, it's important to note that the clock functions just fine, it just no longer adheres to a strict 24 hour cycle. The idea that more blue light throughout the day, beyond the morning zeitgeber, would have an effect on performance is very different idea. To my knowledge, there is not any evidence that this would be the case, and it is contrary to my understanding of Human Circadian Rhythms.