Do you mean white, or yellow/brown?  Most white pines have needles with a white stripe on the green needles.  The needles that are turning yellow/brown looks more like normal life cycle.  Is the aspect that you are showing face north? Needles that don't get adequate sunlight will die back.  The newer growth looks quite healthy.  The plant is evergreen but that doesn't mean that all the needles will live on the plant indefinitely.  Some of the older needles may have been stressed from the extended dry period this summer.  If you are really concerned you can contact a certified arborist to review your plant. 

Unless it is losing needles on the most recent growth, I'm not sure there is much to be worried about.  I would leave it until next spring/summer but make sure your tree gets five gallons of water/week starting in late spring/early summer during it's growth cycle and continue all summer until the fall rains start.  It typically takes 2-3 years for trees to fully establish to weather the dry summer months.