I ditch the white sheets. I layer a lot of cardstock on my layouts and they can get a big thick. I don't need the extra bulk.
When I start to work on a new layout I put one of the white sheets on my scrap table and arrange my photos, embellies, etc. Then after that I can match my patterned paper and cardstock becuase the colors kind of jump off the page at me.
Then I transfer everything to the paper I've chosen and put the white paper aside to start my next layout.