Communicating something important with color alone is a problem for users with poor color vision. So when you indicate something meaningful in an interface with just color, you are creating a poor user experience for about 8% of the male population and 0.5% of the female population.
Color deficiency is complex. The colors that a user has difficulty distinguishing are based on their type of color blindness. Using the example in the photo, we have two coffee pots representing supposedly two different kinds of coffee and different brew times. Both coffee pots are using the same visual signifier on the handle, colored differently, to indicate the type and time of brew on the wall. Which one is decaf? Which one has been brewed at 11:15?
How can this be solved? Don’t use color alone as an indicator. One shape can be a rectangle. The other shape can be a circle. Maybe the rectangle is regular coffee and the circle is decaf. So we would need to write the brew or blend not only on the paper shapes on the handle but also on the key on the wall listed brew and brew time. Otherwise, you would need to look at the chart to figure out which is the coffee that will make your day a +1 day. If you care about brew times, you can look at the chart. Or better yet skip the shapes and use the text “regular” or “decaf” or “hazelnut” if hazelnut is your bag. Most likely it is early in the day and you need coffee like right now so that you can go to a committee meeting. And hopefully the right coffee is in the correct pot or you’re in a 2-hour meeting fueled by decaf. Which either fuels poor team dynamics or is the kindling for a rage quit scenario.