The red dots indicate I'm out of that part of component and the yellow dots for pieces I'm running low on. When I was working on a prototype one time I looked at the drawers and didn't order a part I thought I had. On the day of putting together my prototype I opened the drawer to find it was empty and I was out of that part. And that's the history of the yellow and red dot labels! The Akro-Mils 64 drawers is the one I use most often, they're great for LEGO pieces too!