I'm clearing my blue (common color for me) box first, then trading in all my blue eggs for pink ones. Then I'm clearing the pink box. Hopefully I'll be well on my way to clearing the gold box by then. I'm not trading in my pinks for blues tho while I'm working on my blue box. I'll cross the pink for blue bridge when I get there. I've noticed that when I trade in my pink for blues, that it slows down my overall box opening speed. I'm opening an average of 4 blues and one pink a day, and with the new egg collecting tasks popping up in the quest line, I expect those numbers to go up even higher.