I have been lately wondering why some websites who rank products associate the red colour to being good and green with being bad. Isn't red usually associated to danger or to something you want to avoid as opposed to green?
Examples:
Rotten Tomatoes - Good movie:
Rotten Tomatoes - Bad movie:
Theverge.com - High score (good product):
Theverge.com - low score (bad product):
Taking the two examples you gave, there are two aspects to it.
For the rotten tomato's example, since the percentage of rotten tomato's is an indicator of how highly rated a movie is, it makes to sense to use the color red as a visual indicator as its the same color as a tomato. So one of the reasons is the branding guidelines would also play a part
The second aspect to it is color theory or color pyschology. The color red is used to denote "hotness" and by using the color red in rotton tomatos, you are technically denoting the movie is very hot now or popular.Similarly for your second example where a popular product is denoted by the red color highlighting its hotness in the market. That said, while green is a primary accent color it also is a color which denotes lack of growth. To quote this article
With the color green’s association with renewal, growth, and hope, often green stands for both a lack of experience and need for growth.
Isn't red usually associated to danger or to something you want to avoid as opposed to green?
This would be a cultural interpretation of the color red. In China, it represents good luck and happiness (Wikipedia). You can see more about what different colors generally represent in different cultures in this Information is Beautiful Infograph: Colours in Cultures.
To look at your two specific examples:
Rotten Tomatoes uses two distinct ratings of "fresh" and "rotten", with a "fresh" movie having a rating over a certain threshold (60%, I think) and anything less being "rotten". As such, these two ratings are associated with a nice plump red tomato or a glop of green goo. They have matches their meter colors as a result.
The Verge uses a scale of scores that is color coded, it is listed on each review page towards the bottom:
You can see that is runs the visible color spectrum with 10 being a "warm" red, and 1 being a "cold" blue. As a result green is lower on the scale.
Here is another article on the color red, from Designmodo: Evoke an Emotional Response: Using Red as a Design Tool. Note that while "danger" is a consideration, it is not universal!
In the end, is the use of red in these rating systems significant enough to produce an emotional response in the user that is contrary to what the designers intended? That is only something that user-testing can really tell you; and given the use of the color and the greater audience I would assume it doesn't.
