Hiding background of custom_field (custom:button-card)?

Here’s what it looks like currently:
2021-10-19 07_41_05-
The “Delta” and graph are custom_field entities.
However, they both got a “box” behind them. Opacity or background-color do not influence them, even a bright red background still has the slightly opaque box in it.
Can anyone tell me if these can somehow be removed?
Also, seemingly at random, when reloading the page, the entire card disappears (I’m using the custom layout-card in grid mode). Reloading multiple times eventually makes it show again.

type: custom:button-card
entity: sensor.blood_sugar
show_label: true
show_name: true
show_state: true
show_last_changed: true
styles:
  card:
    - background-color: |
        [[[
          if (entity.state < 75) return 'rgba(255, 0, 0, 0.4)';
          if (entity.state >= 75 && entity.state < 80) return 'rgba(255, 255, 0, 0.4)';
          else return 'rgba(0, 255, 0, 0.1)';
        ]]]
    - font-size: 12px
    - font-color: white
  grid:
    - grid-template-areas: '"n n n" "s i i" "s i i" "l l l" "delta delta delta" "graph graph graph"'
    - grid-template-columns: 50% 20% 30%
    - grid-template-rows: 10% 15% 10% 20% 5% 50%
  name:
    - font-size: 16px
    - align-self: left
    - justify-self: start
    - padding-bottom: 4px
    - padding-left: 12px
  label:
    - font-size: 12px
    - align-self: middle
    - justify-self: center
    - padding-top: 4px
    - padding-bottom: 4px
  state:
    - font-size: 30px
    - justify-self: start
    - padding-left: 16px
  icon:
    - height: 40px
  custom_fields:
    graph:
      - padding-left: 5px
      - padding-right: 5px
      - filter: opacity(100%)
    delta:
      - font-size: 10px
      - align-self: middle
      - justify-self: center
      - padding-bottom: 4px
      - padding-top: 4px
custom_fields:
  graph:
    card:
      type: custom:mini-graph-card
      entities:
        - sensor.blood_sugar
      hours_to_show: 12
      points_per_hour: 12
      height: 80
      hour24: true
      show:
        name: false
        state: false
        icon: false
        labels: false
        points: false
      color_thresholds:
        - value: 75
          color: '#ff0000'
        - value: 85
          color: '#ffff00'
        - value: 100
          color: '#3030ff'
  delta:
    card:
      type: custom:button-card
      entity: sensor.blood_sugar_delta
      attribute: change
      name: Delta
      label: |
        [[[
          var delta = states['sensor.blood_sugar_delta'].attributes.change;
          if (delta > 0) return 'Delta: +' + (delta);
          if (delta <= 0) return 'Delta: ' + (delta);
        ]]]
      show_label: true
      show_icon: false
      show_name: false

I’m not sure what box you mean. Do you mean frame of the card?
Since delta is custom card, you can control its styling in styles: card: section of this card as well as with card-mod. I achieved completely transparent nested cards this way:

  styles:
    card:
        - background-color: transparent
  style: |
      ha-card {
        box-shadow: none;
      }

I think I have done the same with mini graph. Paste later

I mean i.e. image
The rounded frame inside the rectangular white box.
I tried adding the style: entry in both the main card and the custom_field card entry, but it made no difference at all.

Edit: Nevermind, I don’t have card-mod installed. That did the trick. Thanks!