I first observed the same symptom several years ago (interestingly, around the same time that this thread was started...) The symptom continues to present itself on an intermittent, non-persistent basis as of today.
I visited several doctors over the past few years in an attempt to understand what this strange new symptom could be the result of, but I didn't find any answers. I visited two Chinese doctors at separate practices of traditional Chinese medicine (TCM) and they were happy to look at my palms and treat me with acupuncture (and take my money in exchange). While this did seem to clear up my palms and keep them clear for an extended period of time, I didn't receive any clear answers as to what the cause was. It's also difficult to say whether the acupuncture was the reason why my palms cleared, since the symptom typically disappears after a few days anyway.
I also visited a physician who works at a standard clinic and practices western medicine. She didn't seem overly concerned by the photos and told me to come back when the symptom was actively presenting itself. Of course, this was impossible to time since the symptom is intermittent and non-persistent, so I haven't been back and I still haven't found any answers.
I'm wondering if this could be "palmar erythema." Some of the photos for a search result on that condition seem to look pretty similar. Another possibility is "petechiae." But I really don't feel qualified to self-diagnose since I am not a doctor nor even a student of medicine. Not really sure what else to do now other than ignore this and hope that it's not caused by anything serious.