I would assume that they have more than six briefs in total.

I think the easiest way to get started is StreetComplete: https://streetcomplete.app/

It will show you places in your vicinity where information is missing, like opening hours of shops, or the existence of ramps at stairs, and you can provide them in a really simple interface. You can filter out questions you don’t like to answer as well.

import re

def is_even(i: int) -> bool:
    return re.match(r"-?\d*[02468]$", str(i)) is not None

By that logic, the average of red and cyan is both purple and lime. Still useless.

The problem is that averaging hue makes no sense at all because hue is not a longest scale.

If you take a red poster (0) and a blue poster (240), it averages to green. Or take red (0) and red (359), averaging to cyan (180).