Having a problem with a gauge

I’m putting together a skin of my own. If I add a gauge to a dashboard with the default skin then it works fine. If I do it with my own skin then the gauge ‘animates’ up to the right temperature when I load the dashboard and then the color part disappears and I’m just left with the bgcolor:

kitchen_temp:
    widget_type: gauge
    entity: sensor.temperature_5
    min: 0
    max: 40
    color: ffffff
    bgcolor: ff0000
    units: °C

This is what I see after the animation bit finishes.

Screenshot 2020-05-31 at 23.53.50

Sorted it. You have to have low, medium and high colors:

    low_color: 00aaff
    med_color: 00aaff
    high_color: 00aaff

These should probably be listed as mandatory.