I made my first today. 
- type: custom:apexcharts-card
experimental:
color_threshold: true
apex_config:
chart:
height: 220
graph_span: 7d # <- One week
span:
end: day
series:
- entity: sensor.lk_wurzburg_weekincidence
type: column
group_by:
func: last
duration: 1d
fill: zero
color_threshold:
- value: 0
color: var(--my-green)
- value: 35
color: var(--my-yellow)
- value: 100
color: var(--my-red)
A lot of trial and error, but it’s all in the topic and the docs.