What Does a Red or Yellow Dot on Your Tires Mean? | It's to help service technicians properly install and balance the tire. Red - flattest/lowest point on the tire. Yellow - lightest part of the tire
Pretty sure it indicates tire repairs/plugs. You can only have so many before it's a safety issue.
Edit: I had to go look this up and I was severely misinformed it seems. The yellow dot indicates the heaviest point of the tire, which lines up with the valve stem. The red dot is the lightest point of the tire. This is used for balancing.
Edit 2: Had to update again. I'm getting lots of conflicting information from different sources and now have no idea. Something with balancing tires though.