1. Are they white or transparent? I plan to use them at work, so I hope they will be invisible.
Not transparent but if you have longer hair they wouldn't show much. These wax earplugs are transparent, so no worries - nobody at work will notice them :) 

2. Would this work for a one year old for plane travel?
These are very soft and moldable. I've found that my son can press them into his ears the best but when I try they will leak a tiny bit. I don't think these will work very well with a 1 year old. From my experience though, traveling with youngsters, a one-year-old with a sucker or bottle nipple should be able to clear their ears just fine. I would try and keep them engaged on the nipple during the ascent and descent as much as possible. Traveling with youngsters is never easy but if your baby needs to act like a baby, let them act like a baby and everyone else can just live with it. Good luck to you! see less
3. Can these be used for infants under 3 months?
Not recommended