Reveal the clues below only as a last resort.
See the code you are entering below or at this link.
There is no hidden buttons, it is more like a map.
Apply the same principle than level 4, but this time look at inconsistencies in the generated map. Yellow points should be around yellow points, and grey ones around grey ones.
When we used buttons, it was easy to identify inconsistencies. But here not click are twice on the same location. A consistent user will define areas for yellow and grey and click in those areas, hence we need to identify the hypothesis with the better defined areas (relative to the other hypothesis).
A practical way to measure this, is to try to predict the color of a new point from the color associated to the others ones. the easier this is, the more the user is being consistent. In machine learning, we train and test classifiers. This is how this level works, as well as the previous sketch and audio level works behind the scene.