Child Has White Hands And Feet. Feeling Cold. Should I Be Concerned?

My newborn baby now 12 weeks hands and feet turn as white as white can go, colourless for a few minuites then return back to normal pink colour, this doesn t seem to bother her when this is happening, it happens on a daily basis and can happen throughout the day, her hands and feet are always cold to touch however even when they are warm they still turn colourless, at 5 days old both legs turned purple and she was monitored in neo natal ward and given a heart scan which came back everything normal, I have never witnessed purple limbs since but now hands and feet go completely colourless? Should I be concerned? I took her to hospital when I first noticed this approx 3/4 weeks ago and they said its just one of those unexplainable things? They ran oxygen levels in blood etc all normal, please advise on what this is . Thankyou