I have witnessed nipple vasospasm quite a few times now.  In every case the
mother had recovered from a bout of mastitis, often repeated.  One of the
women had acute pain when nipple flushed back through blue to pink after
blanching, a mother that I am currently in contact with has the pain upon
blanching and pain decreases as it goes into blue-pink.  The term describing
the colour change is triphasic - when I first witnessed this happening to a
mother, having seen or heard of it before I nicknamed it 'traffic light
nipples'.  At one point the blanching went almost a green tinge - I have to
admit they never went orange but you get why I called them after traffic
lights because they changed colour/shades before my eyes.

A long article titled 'Nipple vasospasm in the breastfeeding woman' was placed
in Breastfeeding Review 1996 and then reprinted with permission in MIDIRS
December 1996, volume 6, number 4.

The above article mentions three possible causes - Raynaud's phenomenon, poor
positioning and precipitation of symptoms by cold stimulus.

Warmth of room and dry warmth applied to the breasts before feeding helped as
did keeping breasts and body warm between feeds.

kind regards
Helen Woodman, NCT Breastfeeding Counsellor, UK