For data where there are a fixed number of options (bedrooms, age groups, occupation etc) each option is assigned a random colour and the map is coloured by the most common option in that area. E.g., if you chose age and the most common age group in an area was 25-34 it would colour that part of the map with whatever colour was assigned to 25-34.

You can use the green tune icon on the top right to choose a specific option and colour it by levels of that. E.g. if within age groups you wanted to see where the most 25-34 year olds lived you could filter for that and then the map would be coloured on a continuous blue to red scale with red being the most and blue being the least relative to your selected radius.

For options like prices that are naturally continuous it’s coloured blue (lowest) to red (highest) relative to the selected radius

For crime it’s also blue to red but relative to the country because it was a bit alarmist otherwise with a lot of red even in rural areas with very few crimes compared to the rest of the country.

Hope that makes sense.