I have a grandma in Jamaica that I spent a summer with. Since she handwashed all our clothes she got my white shirts really white. Like so white once I got back

I have a grandma in Jamaica that I spent a summer with. Since she handwashed all our clothes she got my white shirts really white. Like so white once I got back to the US everything else looked yellow. I was never able to find what she used at home once I came back to the US so I thought it was this, TSP. Turns out that adding a little bit of blue dye to whites makes them extra bright. And I do remember the blue box next to the wash. So your clothes aren't dirtier, they are stained. They naturally stain since white isn't a natural color (just ask Apple).