Yup displays social value with colors. Rated content and users are underlined with their rating color in the extension and the web application. Each color represents a percentile value in relation to everything else in their category.
The rating system uses five colors, corresponding to quintiles:
Green: top 20%
Yellowish Green: 20 - 40%
Yellow: 40 - 60%
Orange: 60 - 80%
Red: 80 - 100%
For example, the color of the most socially valued Tweet is green.
...and the least valuable is red.
Content becomes greener when it is rated positively and redder when it is rated negatively, reflecting an increase or decrease in the content's social value.
Content has a different color rating for EACH rating category. To determine these percentiles, content is judged against other content's rating in that category.