I used to love them, but it’s over now: diverging red-green color scales.
I bet the reason for the popularity of red-green color scales is that they are so easy to interpret (at least in my culture). Green means good, red means bad. For instance, the above map shows the income of private households for European regions. I used a diverging color scale to show the difference from the average income (bright yellow) with higher incomes in green and lower incomes in red. In fact, I picked the exact colors from good old flare visualization toolkit.
But there’s some trouble with this scale. Firstly, as alluded to above, the meaning of red and green vary a lot in different cultures. According to this helpful collection of Color Meanings By Culture, green is negatively associated in some Eastern cultures like China or Indonesia while red is associated to love, happiness and a long life.