Copernicus Sentinel-2, ESA - https://scihub.copernicus.eu/dhus/#/home

 The pinkish orange grains are probably feldspar and most of the white ones I assume, are quartz. Since there is not a lot of wave action I don't think that the white sand from Meeks Bay would be because of Feldspar being broken down and leaving the quartz behind. I am assuming it is because the beaches are replenished from streams that flow through different drainages composed of rocks of different composition. That is an assumption.  I never hiked up the drainages or took photos with the intent of looking for evidence of that.

   Another possibility is that sand that was primarily quartz was trucked onto the Meeks Bay beach to  offset erosion.  Baldwin Beach has a larger stream draining into it and the beach is less affected by development.

  Sounds weird but Waikiki beach used to import sand from California in the 1920's and 30's to replenish their beaches.   https://beatofhawaii.com/waikiki-beach-a-man-made-shorline/  so I suppose sand could be trucked into Meeks Bay."  STEVEN STUART