Milk caps are different colors and denote fat content. However, between brands the cap colors for each percentage of milkfat aren't the same color.
I first noticed and wrote about this issue in a blog post in March 2018. Since then, I've crowdsourced data on milk caps and continued further work on the project. Here I feature a few projects that have spun off of my milk caps research.
The project as a whole is still ongoing. You can help out and contribute your own milk cap observations!
R Shiny app (hosted on shinyapps.io)
This app was built in order to allow interactive visualization of the milk caps data. It allows the exploration of milk cap colors by state. If it stops working, it's probably because I ran out of free uptime on shinyapps.io, but you can build and run the app yourself from my Github. It's still currently a work in progress. I plan on adding more features, primarily an easier way for people to contribute their own milk caps observations.
Milk Caps Presentation
I gave a short informal presentation on the milk caps issue and an analysis of the data as a whole. All the data and scripts used to generate these figures are on my Github.