Via  bug 679560 

Right now the algorithm is just a simple linear scale from white (0% subtests passing) to green (100% subtests passing). The algorithm in pseudo-code is:

passing = (number of passing subtests for one test_file)
total = (total number of subtests for one test_file)
pass_rate = passing / total
luminance = 100 - pass_rate * 35

In CSS: `background-color: hsl(129, 85%, {luminance}%);`

foolip@ pointed out that we should make 0% passing, 99% passing, and 100% passing more visually distinct from each other. Here are the options discussed:

Current options:

- Red-yellow-green
  - 0% passing = red
  - 50% passing = yellow
  - 100% passing = green
- Red-green
  - 0% passing = 100% red
  - 50% passing = 50% red
  - 99% passing = 0% red
  - 100% passing = green