Here is another real life example after my Another (good) example of (bad) UX design.
Do you want some water? Put the glass in the proper place and push one of the two buttons over the glass: one is supposed to give you cold water, the other water at room temperature.
Now the question: which is the button that gives you cold water? The white one or the blue one? Pick your choice 🙂
p.s. And don’t ask me about the small round red button next to the glass: I’m too scared to push it!